I regularly run two game jams:
GAMES MADE QUICK??? is a low-pressure, week-long jam concurrent with Games Done Quick, intended to spur me into doing something other than watch Twitch for 168 consecutive hours.
Strawberry Jam runs the entire month of February with a simple goal: make horny games. It's judged, but the judging isn't very serious and there are no prizes or anything. I also have a collection of every finalist (top three in any category) from every Strawberry Jam.