Leaving London July 2 and visiting Windsor Castle. Any suggestions of other attractions, activities? Next day traveling to Cotswolds; so we need something in the surrounding area. Thank you.
We took a boat along the Thames from the pier at Windsor - a very good ride with lots to see - see - [original link]
Windsor Great Park, the Savill Garden and Valley Garden. (The Valley Garden is free). [original link]
To add to the other suggestions, you don't say by what mode of transport you'll be using but Runneymede is on the way to Windsor if you have a car. It's where King John sealed the Magna Carta in 1215 and the birthplace of English democracy giving up the "Divine Right of Kings" to do whatever they want. These days it's an open parkland with a pretty stretch of the River Thames running through it and the John F Kennedy Memorial set back from the road behind some trees up a hill.
Windsor is also great for shopping but the Castle and a River Cruise will take up a whole day..
I, too, suggest Runnymede to see a very historical site :
Have a great trip to Windsor and the Cotswolds!
The French Brothers link that Brittania2 provided offers "upstream" and "downstream" boat trips. The "downstream" trip goes to Runneymede if you don't have a car to do it on the way and are taking a train or other public transport to Windsor.
Definitely Hampton Court Palace easily accessible from Windsor and totally different from Windsor Castle
The boat trip along the river sounds good. I made a boat trip on the Thames last year and really enjoyed it, even though i lived in London for several years and know the capital quite well.
If you have children Legoland is not far away.
You could also take a tour of Windsor and Eton Brewery