Fast food places are almost always hiring.
Nursing homes are a good place to look, even if you are working as a dietary aide, it's still very rewarding.
Grocery stores tend to have a high turn over of employee's, might be good for an after school job.
Gas stations (although they might have restrictions on how old you can be before you can sell alcohol and cigarettes.)
I would just start cold calling and see if there are any openings.