Algebra Online
(Questions and discussions relating to all levels of mathematics
[not just Algebra] are welcome):
http://www.algebra-online.com/

Flashcards for Kids:
http://www.edu4kids.com/math/

BasketMath Interactive:
http://www.scienceacademy.com/BI/index.html

Ask Dr. Math:
http://forum.swarthmore.edu/dr.math/

The Math Forum:
http://forum.swarthmore.edu/

(K-12 Math Resources) Dave's Math Tables:
http://www.sisweb.com/math/tables.htm

(Math Reference Tables) Math Archives:
http://archives.math.utk.edu/topics/

(Mathematical Resources) Storybook of Geometry:
http://library.advanced.org/3654/Contents.htm

(Real World Geometry) Math Forum Geometry Links:
http://forum.swarthmore.edu/geometry/selected.geom.html

Math Forum Internet Math Hunt:
http://forum.swarthmore.edu/hunt/ 

Webmath (An online "math engine" step-by-step
solutions to many different kinds of math problems):
http://www.webmath.com/

Graphing Applet
(This applet allows one to enter and plot functions of one variable.):
http://www.pa.uky.edu/~phy211/graph_applets/plot_graph.html

A+ Math:
http://www.aplusmath.com/