Haha college life can suck for the first year! Cramped rooms and crazy roomates. Anywayz my answer to your question also depends on how much room you have and if you're a keyboard player or a piano player.
If your room was like my first dorm and the amount of room you have is pretty much a desk, then you'll want a MIDI controller, like what was said before. Those can be pretty expensive, but if you just want the bare minimum to input chords then I recommend:
The Creative Prodikeys keyboard.
http://www.amazon.com/Creative-Labs-70CF004000010-Prodikeys-Pc-midi/dp/B000E3E888/sr=8-1/qid=1157582720/ref=pd_bbs_1/104-2713663-1298345?ie=UTF8&s=electronics
This is a Keyboard/Keyboard meaning its both a computer keyboard with a musical keyboard attatched to the bottom that, when covered, acts like a wrist guard. This makes transitioning from your homework to music VERY simple and easy. I loved this keyboard when I didn't have room. And for only $50 its pretty good compared to a fancy MIDI controller that can easily hit $200.
Now, if you have a lot more room than that, are a keybaord player, and still just want a bear minimum, just go for a cheap keyboard. It'll serve well in the long run. A cute little Yamaha or Casio, again as said prior to this post, will be fine.
Finally, if you're a piano player, AND have room, I STRONGLY recommend not going down for anything less than a weighted keyboard/controller. A keyboard player vs a piano player are considerably more different than most people think because of the techniques and feel of each. I recommend a Yamaha P-series for the best sound. This option is a lot more longterm. So without knowing what you want your music future to be, this might just be completely too expensive and un-nessecary.
So, I hoped this helped. Goodluck at college!