Wow... another helpful site. Just think of the resources we have today compared to even ten years ago!
For years I've recommend the Christian Research Institute as the place to go for information on apologetics (defense of the faith) and cults.
But as of today, I've found a second site that seems every bit as helpful and as biblically sound (at least from what I've read there so far).
Check out Christian Apologetics and Research Ministry (CARM, for short) at http://www.carm.org/ (just in case their name-link doesn't work).
It's user-friendly, well organized, and had information on just about every cult or false teaching out there, as well as sound answers for seekers about biblical Christianity. It also has thorough research sections on apologetics and religious movements.
It's worth a look. I hope you find it helpful.
[Disclaimer: I haven't read every page on every topic at this site, so I can't know everything said or cited there. But from what I see so far, CARM is biblically solid).