Ludum Dare 42 is coming up! Ludum Dare is one of the biggest and longest running online jams in the world. It brings out a ton of amazing talent to spend a weekend making games and having a good time!
Ludum Dare has 2 formats:
Compo which is solo, 48 hours and everything for your game (except fonts) must be made during the jam time by you. It's considered hard mode, although it is the original rules for LD.
Jam which is with teams, 72 hours and anything goes concerning what assets you can use. The only restriction is that you can't have started making the game before the jam time.
Ludum Dare is a lot of fun and definitely worth checking out if you're looking for a large, competitive jam.