I also love the one-page RPG Jam. It's a jam, though, were there are so many examples of a thing out there that you really can take the idea and make it your own. But political ones are always interesting to see. The Anti-Capitalist one was fun and so was the TittyRPG one. I didn't participate in the later but it prompted works that I felt had artistic value in that they made you really think. Both did.
As a part of jams I think that adding ratings as an aspect are helpful for getting people to explore one another's games. It just takes one or two people to set the example and others begin to follow because the behavior has been modeled for them. I also like jams with charity bundle aspects when the charity is legit and doing really good work.