Explore the Nature of Science through Simulation
Visit the blog.
This is the "temporary" portal to an NSF-sponsored project. The PI is Tim Erickson (tim, eeps, com, connected the usual way). The project is stalled for a number of reasons that practicing educators can imagine all to easily, but fortunately the system works.
So for now we're offering it free. Use the August 2008 version. Go ahead and sign up to be a premium user. Don't give any real credit-card information, just a real e-mail address. You'll receive a confimation code. Use it to set up your premium account!