Splash! Learning Unlimited Programs led by college students for middle and high schoolers

Learning Unlimited incubates and provides a national support structure for independent, college-student-led educational programs aimed at middle and high school students.

Splash is by far the most common Learning Unlimited program; it's a weekend-long extravaganza of classes at a local college or university, where pre-college students are invited to learn about everything and anything from passionate university students. 

http://www.learningu.org/current-programs/about

If you click on the link above and scroll down, you can sign up for the newsletter to find out about new programs in various states.  

General Information about Spark (for grades 7-8 only)

Spark is a short program designed to give our students the opportunity to explore a wide range of subjects. MIT students and community members teach a variety of classes, from urban orienteering to mathematics to Chinese brush painting and everything in between! 

http://esp.mit.edu/learn/Spark/index.html

Splash (for grades 9-12): http://esp.mit.edu/learn/Splash/index.html