11.27.06
SPOJ!
…is the SPhere Online Judge, which consists of a set of programming exercises, and a system for automatically judging the correctness of submitted answers (which may be written in any of a very large number of languages; they even have one of my favorites—PostScript®!).
After a quick scan, a couple projects that caught my eye were Hotline and The Next Palindrome.
Discovered via Digg.