LIVEMOCHA:
One of the most difficult things to practice online when you learn a new language is speaking and reading.
However, with Livemocha not only do you have access to English lessons, but you can practice reading and speaking with real English speakers afterwards.
Livemocha focuses on learning English with real people through their online community, which is exactly what makes this site unique.
To get a language partner, you have to help someone else learn your native language. So you get to learn English, and you get to help someone else as well!