I worked full-time (or close to it) going through school, so I've had lots of non-career jobs along the way.
Working in a Subway was useful, if only for the free food aspect which helped the living-on-my-own budget tremendously. The downside, of course, is that I refuse to eat in Subway for at least another 10-15 years while I wait for the overexposure to their food to burn itself out.
Working in a coffee shop was awesome -- hot co-workers, plenty of regulars to get to know, and, oh yeah, FREE COFFEE. If you're as much of a caffeine freak as I am, that's a major plus. The downside is that mornings are the best shift for making a lot in tips, and you are probably in school at that time.
I tutored for several years, and miss it a lot. You make a lot of money per hour if you're at all qualified, but there is a limit to how many hours you can work per week because of the nature of the job. (Monday through Thursday, considering travel time from job to job, you'd be lucky to fit in two or three appointments per night. Weekends you might be able to tutor more/longer, but there is a saturation point for both you and the student that makes marathon sessions unproductive. Friday night? Forget it.) If you are severely limited in your available hours, and you have some people you can start with to get the word of mouth started, consider it -- it's a rewarding feeling to see your students develop and succeed.
I wish my current job would allow me to go back to tutoring, but my travel schedule is wildly unpredictable. A co-worker and I were doing free drop-in tutoring at Loyola Marymount University for the first couple of years at my current job, and it was a lot of fun. It was nice to be able to teach and NOT have to charge anything.