the Gamemaker Community does an unofficial game jam every 4 months. It's a much smaller, but very well organized jam called the GMC Jam, (and yes, it took a long time to get its formula working so well.) There is a clearly defined set of rules regarding how many persons per team allowed, rules regarding start and end dates, and plenty of time to play and rate all the games. (I don't see how anyone can play and rate 194 entries in 3 days.) The community is very supportive and you get informative criticism and encouragement. I recommend you hang around the Gamemaker Forums and check it out. We just finished the GMC41, so the next one won't be for a while, but you won't regret it.