Summer with nothing to do...Improve college chances?

You don't have any activities related to science or math, but you're planning to apply to top science schools. The least you need for those is something like a science club, and half the kids who get into CalTech each year have already done original research with a college professor. To have a shot at those schools, that's the kind of thing you should have been doing this summer - but unless you've got a connection at a university, it's really too late to try to get something like that.