Well, if you're just looking for a place where a girl is guaranteed a hook-up, I'd say don't stray far from the midwest and head to Rolla, MO. Home of the University of MO School of Engineering. Those guys host some of the wildest parties any college town has ever seen. They're best known for their St. Pat's bash, but the end of the year one is pretty big too.
As far as outside the midwest goes, it's pretty fun down here in St. Pete. St. Pete Beach is always hopping, and you can see some of the most gorgeous sunsets ever. Course, you can then drive 3 hrs and see the sunrise.
Channelside, over in Tampa, is really cool. That's where the cruise ships let out, and there's some great nightlife over there. Ybor City is also supposed to be fun, but we haven't gone there yet, since it's kinda far to drive home after a night out (about 35-40 minutes through traffic for us, tough when you're exhausted!) That's all I can think of off-hand that hasn't been mentioned yet.