The Math Forum
http://mathforum.org
This site, sponsored by Drexel
University, offers "Problems of the Week" in algebra,
geometry, discrete math, trigonometry and calculus, elementary
level topics, and middle level topics.
CyberCalc Index
http://www.npac.syr.edu/REU/reu94/williams/calc-index.html
This site offers a basic review of Calculus
WebMath
http://school.discovery.com/homeworkhelp/webmath/
This site is has a great breakdown of skills
and information.
What Good is Math?
http://www.richmond.edu/academics/a&s/education/projects/webunits/math/home.htm
This site includes some real life examples
where math is used.
Ask Dr. Math
http://mathforum.org/dr.math/drmath.high.html
Dr. Math has some very good explanations of
difficult high school math problems.
About.com
http://math.about.com/
About.com hosts a site with extensive
tutorials and problems
High School Math Hub
http://highschoolhub.org/hub/math.cfm
This is an area with a wide variety of links
just on high school math.