Check Ebay, CL, and local garage sales if you're looking for a college bike.
Don't get anything really fancy for a college commuter. Assume that campus bikes are theft targets, and you'll keep yours a lot longer.
Make sure you get a good lock and learn how to properly lock up your bike.
If you get something nice, consider "unbranding" it to make it low-key. I never had problems with people messing with my bike through 4 years of college and 5 more of commuting in the same town. Unbranded frame and components, locked up like crazy.
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"I feel like my world was classier before I found cyclocross."
- Mandi M.