The most successful mentoring project I did with kids was the Teen Technology Committee at an East Harlem organization (NYC). We met once every two weeks, set up shop on the Web, had an online club with email and chat, we came up with projects integrating the arts and technology, and the best activity was our sleepovers.
I think we had two or three before I moved up to Boston. Kids would get permission from their parents and spend Friday night learning BASIC, HTML, digital video production and photography, graphic design, and creative writing. I mixed in DVD/video movies and lots of food. It was amazing to see teens from 13-18 in their pajamas, learning how to program on a Friday night and having fun doing it even until 2 AM!
"No matter who you are or what your age may be, if you want to achieve permanent, sustaining success, the motivation that will drive you toward that goal must come from within." - Ultramagnetic MCs