Yo, Nightcrawler-
IIRC you're a college student, which (to me at least) equates to being a shooter on a budget.
In that case, I wouldn't go with something like a .40, .45, or 10mm.
If you do some price checking, 10mm runs about $140 for 500 rounds, and .45 is about $119 for 500 rounds.
.40 S&W is only slightly better at about $100 for 500 rounds.(Prices taken from ammoman.com)
9mm, on the other hand, can be had at around $70 for 500 from Ammoman, or you can go to Wal-Mart and get the 100 round value packs for about $10 a pop.
There's no use in having a pistol in a caliber that is expensive to feed, because then you don't get nearly as much practice, and saving for ammo becomes an ordeal. (you can only survive on ramen noodles for so long.)
Also, for your next purchase, you may consider picking up a pistol in .22lr. Granted the cool factor is kinda low, but the .22 is the best round to practice with, it's cheap, abundant, and it's low recoil and easy controllability makes it a lot easier to practice all the basic stuff like site picture, trigger control, stuff like that.
At any rate, don't stress over it too much, and don't let those of us in the chorus distract you by shouting too much advice.