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...
Other
Center School District: Everyday Math Resources
Everyday Math Resources for 5th grade is an excellent resource for both students and teachers. Twelve math strands are linked to activities and interactive games that support the learning outcomes. Click on links at the top to access...
National Council of Teachers of Mathematics
The Math Forum: Famous Problems in the History of Mathematics
On this site, there are several math problems to explore and solve. Look through some solutions by famous mathematicians and expand your thinking about some interesting math concepts. Teachers of elementary grades may want to use this...
University of St. Andrews (UK)
University of St. Andrews: Mac Tutor History of Mathematics Archive
The University of St. Andrews, Scotland, presents hundreds of biographies of famous mathematicians, histories of math in various cultures, and interesting facts on the development of important math concepts. This is a huge reference....