http://lang-8.com

Lang-8 is a social networking site for language exchange and international communication. At Lang-8, you can write in the language you are learning, have them corrected by users whose native language is the one you are studying, and then help other people that are learning your native language.

Lang-8 makes language learning fun thanks to the social aspect! Make friends and learn about their lives while learning and practicing a new language. Lang-8 makes it easy to learn, and you'll always want to come back to practice! (less info)