Two more potential "unschooling" resources to consider:
MIT's Online Education Prototype Opens For Enrollment
The above Slashdot title is self-explanatory.
I've also recently found another simulation system: NetLogo. I've played with a couple of the biology simulations, and they seem pretty solid. There's tons of other science simulations, both in the built-in library and in the online database of community contributions. I haven't done any programming, but it looks like it could be a rather simple (and quick feedback) system to practice the basics of computer programming.