University of Regina (Canada)
University of Regina: Math Central: Quandaries and Queries at Math Central
Students can post a question about Math here and someone at the university will reply. There is an extensive list of questions that have been asked and answered already, arranged in alphabetical order by topic.
National Council of Teachers of Mathematics
The Math Forum: Student Center
The Math Forum Student Center provides math news, notes, challenges, and much more. Dr. Math is here with the answers to students' math questions. There's a teachers' section, a research division, and a parents' part. This site also...
Wolfram Research
Wolfram Math World: World's Most Extensive Mathematics Resource
MathWorld provides a huge mathematics encyclopedia detailing the concepts of geometry, algebra, calculus, discrete math, number theory, and other math topics--complete with formulas, diagrams, examples, and references for thorough...