Campus work study when I was still a student, then got hired on by a pair of professors to assist with their research after graduation. It was a wonderful experience -- after the summer they wanted me to come be a grad student in their lab for $20k a year, I sort of had other aspirations in life, we parted ways amicably.

Failing that there is always retail/food service/etc, but working on campus has a lot to recommend it over these other options. It pays better, is more convenient, has more potential to result in something with resume power, etc.