Kelpy, I was in the same situation a few years ago. I ended up going to my LBS and buying the second-cheapest bike there. It was a Giant MTB with absolutely nothing special except a cheap front suspension fork. Cost me $150 IIRC, and with the shop offering free tuneups and whatnot. Used it for three solid years, left it in the rain with a bag over the seat, barely did any maintenance. It never got hassled by thieves, and I always locked it up with a U-lock + cabled front wheel. Worst that happened was one day I left some accessories on and they got stolen.

So, I'd suggest walking into your college's LBS and see if they have any REALLY CHEAP bikes for sale. If it's a college town, they may well.

(edit) Plus, I still have the bike. I have since gotten a new one though