The summer after my freshman year in college was spent working at a Cumberland Farms store (think gas station/store) right off of Narragannsett Beach. The job wasn't hard, the money wasn't great, but I learned TONS in terms of taking care of supporting myself (I didn't move back home).

To the original poster, I immediately thought of resort towns and the service industry as they are always looking for seasonal help. Considering you are looking for lodging as well, what about summer camps?

Michelle