Dungeons and Dragons
We concede that the students that attend OWL are a diverse group, and this sometimes means pretty nerdy and/or geeky (and yes, there is a difference).
One of the things we have is a Dungeons and Dragons (D&D) group that meets after school.
Believe it or not, there are curricular tie-ins as well. Students are currently working on a PC generator to assist new students in creating their own characters so the understanding needed to join is much lower than it would be otherwise.