A quick shout out to Peer 2 Peer University - a really neat project focused on creating an open online community for continuing education. Their classes are super intensive (think six weeks and college-level), but they're also free, which is, I think, the best combination ever.
The next batch of classes start September 15, though you've got to sign up by September 8 if you want in. A couple of my favorites are this Creative Nonfiction Workshop, DIY Math, and a wicked Intro to Music Theory. There's also a ton of web and programming related courses, so yeah, pretty much anything you want.