Recently I started using the Lang-8 account I signed up for ages ago. Basically you post a journal entry, and it gets corrected by native speakers. The idea is that you go and correct articles of your native language in exchange for corrections on the language you're looking for. You get friend lists as well, so if you are social, more people will see your entries on their friends feed as well as the public feed.
The corrections are done on a line by line basis. Usually you will get multiple people correcting your Japanese, and you can pick the corrections that make the mot sense to you, if there are more than one. Corrections usually come VERY quickly due to the amount of people using the recent post feed!
I've done 2 posts so far and continue to do more!
So go forth, and BE CORRECTED!