There’s been an explosion in the number “social network” language learning sites that have started over the past year or two. A primary purpose of these web applications is for native speakers of a language to connect with others who want to learn their language and help them do so.
I have a number of pedagogical and safety concerns about using these sites in the classroom. However, a very small number of them — most notably the excellent Live Mocha site — offer exceptional interactive teacher-created exercises and activities that are unique and beneficial.
A new one that isn’t in Live Mocha’s league yet but which has some potential is called Busuu. It has a lot of good activities members can use without necessarily participating in the “social network” aspect of the site.
I’ve placed a link to Busuu on my website under Vocabulary.