I'm in Saint Louis. Today is very mild, but thats cause its 1:30 right now and its really dark outside, and we had a cold front last night.
Anywho, Saint Louis is a good place. I used to hate it, but its been growing on me.
First off, you need to see Forest Park. Wait for a day that is relatively mild and nice out (you don't want to die if you aren't used to the heat like us residents are). Art Hill was recently redone and is absolutely beautiful. The park is huge enough to spend an entire day in, just wandering around.
Also, the Delmar loop. Shopping district, really good resturants, a good venue, and a great independant theater (the Tivoli. You will recognize it because the sign looks like a giant penis, and if you read it from down to up, it says "I lov it")
They have great films, the midnight films are especially fun (Saw Resevoir Dogs last saturday . . . sunday morning).
A couple of other good theaters. Webster University is in Stl, and they have a great drama program, so its worth checking out what they are putting on. You can bike the Katy trail. Its huge, and straight and flat, with good scenery. You can just go forever on that trail. Right through missouri wine country, if you need refreshments.
Also is Babler state park. Just a huge hilly forested area with lots of trails. Beautiful.
And you can do all the tourist stuff, like the zoo and the arch.
The art museum is quite good, if you are into that kinda thing.
The Landing. I'm 18, so I don't really spend very much time there, but they have a GREAT venue called Mississippi Nights. Great music. They also have lots of the better local bands play there. Parking isn't that bad, there is a huge attended lot across from Mississippi Nights. Its a bad neighborhood, so don't go wandering the streets at 3:00 AM. Attended lot is a must.
I almost forgot the Botanical Garden. Its great. Huge, lots of different areas, lots of cool architecture mixed in with the plants, just a huge landscaped park. You gotta pay to get in, though, which is kinda a drag. If its really hot out, wear swimming trunks and a T-shirt, because they have several fountains the encourage people to get wet in. On a hot day, you will welcome it. If you have kids, they have a medium-sized hedge maze that kids love. You can play the minotaur and chase them a bit. My 6 y.o. sister loves that.
Saint Louis is a good place.