math.com
A very comprehensive site – there is help with basic math, algebra, geometry, trigonometry, calculus, and more. Again, though, be careful to follow links that are part of the site, and not other ads. Stay to the “Select Subject” menu on the left.
Open Link
WebMATH
This is a really good site, because it lets you type in a math problem that you’re working on, and then it gives you a step-by-step guide on how to solve it. The site covers general math, algebra, geometry, calculus, and other stuff.
Open Link