What can cause stress with college students?

Anything.

To elaborate on what Smoothy said, there is a long list and what on there is as unique as the person it belongs too. There is a common subset though:
1). Relationships
2). Money
3). Marks/academic achievement.
4). Drug/alcohol use
5). isolation
6). Body issues (Freshmen 15 anyone?)

Life is stressful. Anything you can think of can be a stressful situation.

Why do you ask this?