Anyone? (I'll post mine after someone else posts so that this isn't just a plug)
I'm just starting one.
My girlfriend and I met on another message board, one devoted to the study of invented languages. For a while now we've been trying to learn each other's languages -- difficult because we're still living ten thousand miles apart from each other -- and now we've thought of a new way of helping us along: we're each going to start a journal in the language we're learning, and use the "comment" feature to correct each other's mistakes.
I won't bother linking, because you wouldn't understand any of it :P