Post in the language you're learning, and get advice from native speakers.
Ranked in these QuestionsQuestion Ranking
Pro Gain experience writing in your target language
Where many programs will have you writing single sentences at most, Lang-8 encourages you to write short stories or diary entries.
Having to actually write in the language rather than simply remember vocabulary is a really beneficial feature for improving real-world use of the language.
Pro Get feedback from native speakers
Native speakers of the language you are learning will give you pointers on your writing, such as grammar corrections and advice on word choice/sentence structure.
Con Not a good starting place for beginners
The site doesn't teach you your language, instead it allows you to get advice on your writing in your target language. It's better if you have a basic understanding of the language at first.