WolframMathWorld While this site is primarily geared toward higher math, it’s an invaluable resource to have “at the ready” for when your student (or you) venture into this level of mathematics. A worthy site to keep on hand!
InteractiveMathematics There is something for those who are learning everything from integers to higher (gulp) calculus here. There is also the option to download a variety of graph paper from the site as well. In addition to the examples, answers and explanations of a wide variety of math levels, there are also some games thrown in, just in case you didn’t get enough math fun in for the day. I love that this site, and all of the other free math sites exist, I just wish all of this free help had been around in my day…(sighs)