These things are all free and accessible online.
On this site
A page on word problems. Everyone tells me word problems are where they meet their match. Here are some methods that make them doable.
A page on very basic statistics. If you know very little about statistics and need to master just a bit of the discipline — say for the SAT — this page is for you.
A free download of Problems Solved, a book that helps you handle common math pitfalls.
Is there something else you’d like to see covered? Sign your student up
Elsewhere on the Web
Khan Academy. This site covers a great range of math, from “early topics” like counting all the way to multivariable calculus and differential equations. Lessons, videos, and quizzes.
Patrick JMT. Math videos. I don’t have a lot of experience with this site, but calculus students have told me they’ve found enormous help here. This site has videos on arithmetic, algebra (lots), calculus (lots), discrete math, linear algebra, prob/stats, trig (lots), and some other things.
Paul’s Online Math Notes. For algebra, calculus, and trigonometry, this site is a one-stop shop for study needs: lessons, exercises with solutions, and cheat sheets. Paul’s style makes the math easy to understand.
Purple Math. Lessons in algebra, organized by level: preliminary (pre-algebra), beginning (Algebra I), intermediate (Algebra II), advanced (Precalculus), plus a little bit of stats and trig. Clear lessons with examples but not a whole lot of practice problems.
Varsity Tutors. Not everything here is free, but plenty of stuff is. Check out Virtual School Day.
VPT Math. For you Virginians out there planning to go to community college, here and here are practice questions for the advanced portion of the test. You can get the more basic part from Virginia Math Placement Test Practice Answers Explained.
Wikipedia. Not a math site, but indeed this site includes a lot of math among many things. Wikipedia is a great reference, with a definition for every term you can imagine, as well as all sorts of formulas.
YouTube. Videos about everything. Math is no exception to YouTube’s posting a great number of videos on every topic. Please see my video on slant asymptotes.