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...
National Council of Teachers of Mathematics
The Math Forum: Ask Dr. Math: Fraction Basics
Gives a very basic overview of fractions and their parts. Discusses adding, multiplying, and finding a common denominator.
Other
Stat Soft: Statistics Glossary
Dozens of statistical terms are defined and illustrated in this glossary.
AAA Math
Aaa Math: Words for Numbers
This lesson explains how to write words for numbers. Includes exercises and games to practice this skill.
Math Is Fun
Math Is Fun: Comparing, Ordering Decimals
This website gives a simple, easy strategy for how to compare decimals when they have a different number of decimal places. It provides examples in ascending and descending order and an ordering game for practice.
Other
Print and Learn: Writing Numbers
This simple website has a printable page for each of the numbers one through ten. On this sheet you can practice writing the digit, the word and the word in a sentence using manuscript printing.