Livemocha.com is my current hobby. The actual language courses they have are all too easy, I think, for anyone who has ever actually taken classes, but they might be useful for picking up something entirely new.
I really like the practice and share sections, where you can respond to writing prompts in whatever language and other users fix your mistakes. Right now I'm working on my Mandarin and Spanish! You can practice speaking/reading, too, but I don't have a microphone so that's out.
Today I went to a farmer's market to buy some fruit, and then I wandered around the National Postal Museum for a little bit. I've spent pretty much the rest of my day on MSN and Livemocha.
Although, I am getting an awful lot of hate for using traditional instead of simplified. Hmm.
I really hate rabid chinese nationalists.