ZetaAce - there is seriously something for EVERYONE in Houston. It's hard to name off just a couple things!
The Zoo and museums are phenomenal. The Space Center (NASA) is really interesting if you are into that sort of thing. Spindletop is a restaurant downtown that rotates for a view of the whole city (especially nice at night when you don't have to look at the smog). Downtown has been completely re-vamped and is now the trendy place to eat and drink and see and be seen.
The Galleria has been mentioned, but is so cool for shopping and people-watching... and be sure to check out the huge Water Wall fountain behind the Galleria, which is super for pictures. Be sure to eat some seafood while you are there, which of course comes fresh in from the Gulf everyday...
whew! That's all I can think of in 30 seconds.
[This message has been edited by Texas Alum (edited December 27, 2000).]