The Princeton Review has an online test prep section for everything from the PSAT to the GMAT (and some I've never heard of).

Registration is required but only took couple minutes; the usual name, address, and email are required.

I started taking the SAT. The instructions were easy to follow and if memory serves (it's been a long time since I tested) it's pretty representative of the real thing. I stopped and marked my place to continue later.

I'll post the results here when I'm done - provided I don't embarrass myself.

-Barry Wynn