BugMeNot - instantly get disposable login details for any popular website that force you to register.
Yak4Ever - make free international calls from US, UK and Ireland to 50+ countries.
UrbanDictionary - hilarious (and practical) 100% user-maintained dictionary where users provide and vote on definitions for urban words (slangs).
BossBitching - fun and active community where people can bit*h about their bosses anonymously.
RateMyDrawings - excellent place to draw, share your drawing creations, learn to draw, and watch other people drawing.
Video demo
Scribd- search, browse, rate, share various types of documents (jokes, facts, stories etc.). It’s like Youtube for text documents.