Interactive, personalized online math instruction used in Mrs. Hubbard's Resource room:
www.tenmarks.com/

Calculator:
http://v2.toolboxpro.org/secure/calculator.cfm

Length converter:
http://v2.toolboxpro.org/secure/length_converter/converter.cfm

The DeciFractor converts fractions to decimals from numbers you input:
http://www.amblesideprimary.com/ambleweb/mentalmaths/fracto.html

Video instruction in high school math (algebra, geometry and higher)
http://www.mathtv.com/videos_by_topic#

Amusement park of fun in math - ages 13 & up (pre-algebra skills and higher)
http://www.coolmath.com/

Explanations, narrations, and illustration to convey key concepts in math. Instruction focuses on pre-algebra and algebra. The lessons in Visual Math are also a useful review for parents trying to help their kids!
http://www.visualmathlearning.com/index.php

Clear illustrations, explanations and interactives all help to make math learning easier here:
Math">http://www.mathsisfun.com/">Math 

MathNerds provides free, discovery-based, mathematical guidance via an international, volunteer network of mathematicians.
http://74.81.197.188/index.aspx

Browse more than 2,500 Math pages filled with short and easy-to-understand explanations.
http://www.sosmath.com/