4 Days

There's so much to see and do, Robb, so it would really help to know when you are planning to visit and what your interests are.  I am also presuming that when you ask about 'Cape Town', you mean the Cape Peninsula and not just the city itself.

My personal favourites (in no particular order) are:

Swimming with penguins at Boulders Beach in Simon's Town

Hiking up Table Mountain from Kirstenbosch National Botanical Gardens and then getting the cable car down

Whale watching in False Bay(mindful that they're only there in winter)

The Two Oceans Aquarium

Wandering through Bo-Kaap (with its distinctive ice-cream coloured little houses)

Hiking the Silvermine Trail and looking down over the Atlantic beaches - particularly Hout Bay

The drive south along Boyes Dr, looking over False Bay and ending up in Kalk Bay

Walking/riding along Noordhoek Beach

The astonishing (and often overlooked) Heart of Cape Town Museum  at Groote Schuur Hospital, where Dr Christian Barnard performed the first heart transplant

Open air concerts in Kirstenbosch National Botanical Gardens in the summer, which take lace against the backdrop of Table Mountain - usually on a Sunday evening.

There is a 'hop on, hop off bus' in Cape Town which covers two separate routes, so you would be able to do most of these even if you don't hire a car.

Hope this is enough to get you started :)

The standard classics:

- Table MountainTable mountain (I would suggest you climb lions head)
- Robben IslandRobben Island (if you like that boat trip, try Hout BayHout Bay and go to Seal Island too)
- Kirstenbosch National Botanical GardensKirstenbosch botanical gardens
- V & A WaterfrontWaterfront shopping center (its just shopping, but you have to say you were there, and Hudsons has awesome burger and milkshakes)
- Boulders BeachBoulders Beach to see penguins.  At the same time, I would drive round to Kalk Bay and walk around
- District 6 museum (and other heritage sites). They have free walking tours in the city that may be worth looking into.  There is also the red bus that is very popular
- I would suggest the Saturday market at Route44 in Somerset West (http://www.root44.co.za).  Also a nice time to drive to other places around that area
- FranschhoekFranschoek wine tasting
- Shark cage diving in GansbaaiGansbaai if you are into that.  
- Paragliding off lions head / signal hill.  Plenty of companies doing that (I would suggest parapax (www.parapax.com), but there are many)
- Clubs in Long StLong street
- Driving from the city to HermanusHermanus and then back around RooielsRooi-Els.  Also the Chapman's Peak DriveChapmans peak drive

This going to keep you busy?  If not, you can start looking at the Garden Route!

Sincerely