I’ll link some contests instead of judges: (I think I’m forgetting some)
Annual competition. Very fun!
Challenge 24 http://ch24.org/
Annual competition. Also very fun
Not only it has a wonderful training site, it hosts competitions every now and then. It starts around november.
SPOJ has a contest page!
High school programming league 2012/2012 is running right now.
Annual competition. The objective is building a player for a game.
Google Code Jam
Facebook Hacker Cup
AI Challenge http://aichallenge.org/
I don’t know if this will be held again there has been three editions, I hope so!
There’s a list! http://clist.by/
This is thanks to ‘aropan’ of Topcoder and Codeforces