What to do over the summer for comp sci?

I want to major in comp sci and plan on aplying to, among other places, CMU, UC Berkeley, Caltech, Northwestern, and maybe MIT or Stanford.

Last year I worked in a lab over the summer at the University of Pittsburgh doing research on neurodegenerative diseases, and if I can’t find anything else that’s what I’ll do this summer too.

Since I like comp sci and am planning on applying with that major, I would like to do something over the summer that fits more with comp sci. Are there any really good programs or similar opportunities that I could do a project on artificial intelligence or something similar that I would enjoy a lot and also would look really good for applying to the top CS college programs??

Look at Hampshire Math , a six week intensive mathematics program, its test in and FREE, on Hampshire College campus in Massachusetts:
http://hcssim.org/

Math skills are much more important than programming skills for most of the top schools.