Imagine Cup is a student competition for developers. You can write an application, or a game. Teams can include high school, undergraduate or graduate students. You may not be a student, but you probably know a professor or teacher or student. Help them start a team, and help them win.
Jennifer did a great job covering all of the details on her blog, so I am just going to send you over there.
http://blogs.msdn.com/b/jennifer/archive/2010/11/02/imagine-cup-become-an-industry-advisor.aspx