I spent about a half an hour reviewing this forum and found it pretty comphrehensive.
They have all kinds of interactive programs to tackle a variety of math, and your personal math problems.
I feel very strongly that the content is accurate and wide ranging in it's ability to help educate a student or someone who wants to sharpen their math skills.
I do think that used appropriately the math forum page is an excellent interactive tool that will both help students and help faculty alike. One reason I feel this way is with peer review and all the resources this site brings to bare it is truly a great source of information to help students.
Ease of use, I'm not the most technical person around, but I thought it was pretty easy to manuever in and around this page to get the information you need.