Write an RPG in 24 hours, during November, in the Pocketmod format, without any numbers. Hard enough for you? Run as part of NaGaDeMon http://nagademon.com
I'm posting this now because I want to start soon ... I just don't want to start now. I already pushed something out tonight and need a day or two to recover.
I also do which isn't much, but it's enough for me.