PurpleMath.com - This website has a great way of explaining how to solve problems, including why it makes sense. They guide you through solving several example problems for each topic. Also a section called "How to suck up to your teacher" Take a look, eh?
KhanAcademy.org - This one has been in the news lately. It's a catalog of thousands of short videos on just about any topic you can think of. The videos are generally between 2 and 10 minutes long.
CoolMath.com - Includes lessons, practice problems, a glossary, and some of my favorite games
Math.com - Lessons on a wide variety of topics. A little cut and dry, but accurate.
Wolfram Mathworld - This site is definitely geared toward higher level math, but they have a lot of good information. While Algebra and Geometry students could benefit from the site, Alg 2, Trig and Pre-Calc students are more likely to find this site worthwhile.
