Best free things to do in Seattle?

Seattle Art Museum and Olympic Sculpture Park, as Adam mentioned, are both great if you can take advantage of the first Thursday timing. I'm also a fan of Alki Beach.

Seattle has a number of interesting galleries that display and sell Pacific Northwest tribal art and crafts, including Flury & Company Ltd and Steinbrueck Native Gallery. 

It might sound a little odd, but I could spend hours in Uwajimaya—they have an incredible array of products and the location on 5th Ave. is connected with a pretty incredible Japanese bookstore—I love the magazine selection. Plus, you can grab a bite to eat for a reasonable price!

Art/Museum: First Thursday of every month the SAM (Seattle Art Museum) is free. There is also a beautiful botanical garden on Capitol Hill Neighborhood that is free to walk through (also provides nice view of downtown). 

Food: grab some tacos at El Camión Food Truck (locations all over), croissant sandwich at Le Fournil Ltd Bakery & Catering (East Lake).  Should also do the Theo Chocolate Factory Tour tour in Fremont Neighborhood.

Outdoors: Do Discovery Park, Golden Gardens (Ballard Neighborhood), Alki Beach (West Seattle), or the garden at Seattle Art Museum.

Check out all the parks! Olympic Sculpture Park/Myrtle Edwards Park, Gas Works Park, the Ballard Locks, Kerry Park, Discovery Park -- all free and all amazing.

Pike Place Market is also a must, if you've never been. 

There's also a Starbucks on the 40th floor of the Columbia Center. While not free, it has AMAZING views and all you need to do is by a drink or snack.

Pike Place Market is always a fun place to visit even if you don't plan on spending any money. If you go, make sure you watch the fish throwing and to visit the gum wall. You can visit Alki Beach and enjoy walking along the boardwalk or play some beach volleyball. Also, the Pacific Science Center isn't free but it's $20 per adult for general admission and you could probably find some coupons.

If you make it down to Tacoma the Museum of Glass is an amazing place to visit and is $15 per adult. If you're really hoping to go to lots of Seattle's museums, it would be a better deal to buy a city pass. They're $69 per adult and it gives you admission to 5 attractions (1- the Space Needle, 2- Seattle Aquarium, 3- Argosy Cruises Harbor Tour, 4- Museum of Pop Culture or Woodland Park Zoo, and 5- Pacific Science Center or Chihuly Garden and Glass). If you can afford it, I highly recommend it (http://www.citypass.com/seattle?mv_source=rkg&creative=56083442909&adpos=1t1&device=c&network=g&matchtype=e&gclid=CNm4qciyn8UCFRaTfgodgRMA2w).

If you're looking for any hikes to do, I recommend any at this link(http://www.wta.org/go-hiking/seasonal-hikes/regional/hikes-30-minutes-from-seattle). If you have enough time to go to Mount Rainier National Park, I totally would. It's about a two hour drive from Seattle and is beautiful this time of year. It has so many different trails to hike.

The Washington Park Arboretum is a beautiful garden with lots of flowers and is completely free. The Olympic Sculpture Park is free also and features sculptures from artists such as Richard Serra, Alexander Calder, Mark di Suvero and Louise Bourgeois.

Definitely walk around the Seattle Waterfront and enjoy some people watching. There's a ferris wheel there that you could ride but I believe it's slightly spendy.

If you're looking to learn some history, go to the Log House Museum to learn about the stories of the "Alki Landing Party" and the Duwamish tribe.

Also, A trip to China town Seattle is a lot of fun! They have many great Asian restaurants there and you get to learn about their culture.

Before your trip, research events that will be going on in Seattle the time you will be there. The city always has many free events for the public to enjoy. There is so much more I could tell you so if you have any questions just ask me!

Pike Place Market is fabulous.  Walking is free, buying anything is pricey (except flowers). There are small shops across the street as well with goodies to munch on.  You could spend hours here, go to: pikeplacemarket.org. Walking along the water front can be fun, but the contruction of a new seawall has closed some of the restaurants and stores.  Still, it gives you a feel of the city.  A bit touristy.  If you want to splurge, try The Seattle Great Wheel.  As a foot passenger, the ferry to Winslow (Bainbridge Island) is spectacular, especially on a nice day - $8 roundtrip collected only on the Seattle side.  You can see Mount Rainier to the south and Mt Baker to the north (on a very clear day). Go up top (outside) and circumnavigate the boat.  If you have leftover lunch, you can feed the seagulls as the ferry zooms along. The town is small but poking around can be great and you will be able to find places to eat that are reasonable (there are some expensive ones, too).

Ballard Locks are really cool and totally free.  There is an underwater window to see if salmon are trying to make it back up to fresh water.  And watching pleasure boats go through the locks is an experience if you've never seen it before.

Enjoy Seattle!  (but please don't move here - our traffic is already terrible!)

Kerry Park is free and has a great view of the skyline for photos

I would second the recommendation of Pike Place Market, its always entertaining and is free unless you give in to temptation!

I would definitely go to Seattle Center, its expensive to ride to the top of the Space Needle but its free to wander around the grounds and look at the Space Needle, and theres usually something interesting going on around Seattle Center.  Also if "next month" happens to be May, and you are in Seattle over Memorial Day weekend the Northwest Folklife Festival is at Seattle Center, with lots of great music, much of it free, and also many food and craft vendors.  There is also the Bite of Seattle in July, and Bumbershoot over Labor Day weekend.   The Bite is all about food but eres usually quite a bit of free music and entertainment.  Bumbershoot is all about music, but there is an addmission charge, and an extra charge to some of the big name shows, but there is also lots of reasonably price or free music.

The Ballard Neighborhood Fremont neighborhood is a fun walk, lots of Scandinavian influence and heritage.

I would also recommend a walk around Pioneer Square, lots of interesting shops, taverns, restaurants, and galleries.  The Seattle King Street Station is also worth a visit.  The station was renovated a couple years ago back to its original style, the high celings, plaster work and chandeliers are beautiful.  

The LightRail or Sounder Commuter Trains are relatively inexpensive, and make for a nice way to get to Tacoma or SeaTac International Airport, and will give you some different views.  A ride on the LightRail will also give you a view of the downtown bus tunnel stations, they are intersting from an art/architecture/engineering perspective.   Although you could just take a walk into one of the bus tunnels for free.  

Westlake Center is a big commercial mall, with many pricy shops, but its only a few block walk from Pike Place Market, and has its own tunnel bus/lightrail station.  There is a typical mall food court on the third floor but theres a nice balcony with some nice views of the outdoor pedestrian area of Westlake Center.  The mall also contains one end of the Seattle Monorail, the monorail isn't free, and is a bit cheesy/touristy but it is kind of an icon of Seattle.   Theres also a Top Pot Doughnuts shop near Westlake, not cheap but great doughnuts and good coffee, but i love the place because of the shelves and shelves of old books.   I was going to pop in just to grab a coffee and doughnut to go but ended up sitting there for an hour pouring through old books!

The REI flagship store is probably worth a visit if you're into the outdoors, although again its only free if you can resist temptation!   Also nearby are several restaurants and shops, including El Corazón, one of Seattles classic music venues; the Lunchbox Laboratory; Feierabend (German Pub); Paddy Coynes Irish Pub; and St. Spiridon Orthodox Cathedral, one of Seattles oldest Orthodox cathedrals.  And then maybe you could even take a ride on the SLUT? South Lake Union Tram ( its technically a streetcar), normal Seattle Metro fares, but its a nice ride along Lake Union, and you could take a walk around Lake Union Park.

If you have time and transportation i would recommend a trip to Snoqualmie Falls over a trip to Mount Rainier. Its much closer, (only about 30 minutes from Seattle)  The falls are beautiful, there are several short trails around the area, and the Lodge at the falls appeared in the old Twin Peaks television series, you might even be able to find Agent Coopers room! 

Last but not least, I love the Washington State ferries, not free, i believe a walk-on passenger ticket is around $10(?) But i love the feel of being on the water, and the views you get of the city, the mountains, and Puget Sound.  The food on the ferries is actually not terrible although it also isnt cheap.  The ride to Bremerton is about 1 hour and to Bainbridge Island about 45 minutes.  There are some shops and restaurants in both Bremerton and Bainbridge within walking distance of the ferry, so it can make a nice lunch break.

Seattle has some great neighborhoods to explore. I would recommend checking out Fremont Neighborhood. You can see the Fremont Troll, a  Statue of Lenin, and a giant planet Saturn a top of a building. There's a wonderful walk along the canal that will take you to Gas Work Parks and great restaurants that won't break the bank. It's a wonderful way to spend a day in Seattle! 

After a cup of clam nectar and an order of fish and chips to share with the seagulls at Ivar's Salmon House on the waterfront, walk onto the Winslow Ferry that docks nearby. In about thirty minutes, you'll find yourself in an island village looking back at the big city. Restaurants, bakeries, bookstores and beach walks beckon. On a sunny day, you'll gaze at the Olympic Mountains to the west,Mount Rainier, the Cascade Range and the Seattle skyline to the east. A round trip costs $8.00.

Seattle Art Museum, Seattle Asian Art Museum, Waterfront Art Museum-free and out doors - all part of SAM

Frye Art Museum (free)

Seattle Aquarium

Zoo

Green Lake2.8 mile walk)

Discovery Park Blvd, Kerry Park, The Gold Rush Museum

I´d recommend amazing views of Seattle:

-Kerry Park  (you can stop by to get a delicious ice cream from Molly Moon's Homemade Ice Cream

- Gas Works Park

-Alki Beach

View from 40th floor Starbucks in Columbia Tower Club

People watching in Capitol Hill Neighborhood

View of Seattle from Kerry Park

A hike in Discovery Park

Samples early in the morning at Pike Place Market before all the people arrive. 

Free sailing trip at the wooden boat museum in South Lake Union on weekends. 

Taking photos of blooming trees in the spring and fall colors in the Arboretum Foundation.  Or just take a walk there in the summer. All the way to the lake. 

Swimming in the lake and people watching at Madison Park beach.  There are also a few nude beaches if you are so inclined. Look them up on Lake Washington. 

Walk the The Conservatory and climb the water tower in Volunteer Park

Coffee tasting at the the Starbucks Reserve Roastery & Tasting Room or better look up with Caffé Vita is doing there free weekend roasting tour and tasting. 

Go to the salmon ladder at the Ballard Locks. Go to the Sunday market in Ballard. 

Phew. This is a great city. 

Seattle offers the best of both universes: a plenty of indoor choices in addition to simple access to the range's hypnotizing incredible outside. After you mark off the Space Needle and monorail, get your dosage of expressions and society; investigate the downtown Seattle Art Museum, Capitol Hill's Seattle Asian Art Museum, the Burke Museum of Natural History and Culture on the UW grounds and, for something other than what's expected, the Museum of Pop Culture in Seattle Center. Open air buffs appreciate Discovery Park and Magnuson Park, the shorelines in West Seattle and north of Ballard Neighborhood, in addition to in the open air brandishes that range from kayaking to oar boarding.  Click here for Seattle Tours information.

Seattle Tours

Take a stroll through Pike Place Market and visit the Space Needle. The walk from Pike Place through Belltown up to the Needle is great. Lots to look at. 

Pike Place Market with all the stalls, street musicians, and fish mongers make for a wonderful stroll. And don't forget the Seattle Gum Wall...