Tricia Howell hit all the common activities when asked what she was doing. I hardly ever party. I'm quieter then that, but I still enjoy summer. I like to write short stories, chat online, and swim with my friends. You don't have to bum it, though.
Summer is a terrific time to accomplish tons of things.
Like getting in shape, for example. Running, swimming, and dancing are all easy, cheap, and great exercises. And hey, if you get good you'll have a team to join at school next year. When it rains, I suggest you paint, design web sites, make clay pots or cook. Of course there is always volenteer work.