Simplifying Expressions
This site gives some practice with simplifying algebraic expressions.
http://www.teacherschoice.com.au/Maths_Library/Algebra/Alg_7.htm

Distributive Property
The key to simplification is the correct use of the distributive property.
http://www.algebrahelp.com/lessons/simplifying/distribution/index.htm

This site gives a nice visual pattern illustrating the distributive property.
http://regentsprep.org/Regents/math/realnum/Tdistrib.htm

Adding and Subtracting Polynomials
This is an interactive site which takes adding and subtracting of polynomials step-by-step.
http://www.wtamu.edu/academic/anns/mps/math/mathlab/beg_algebra/beg_alg_tut27_addpoly.htm

Multiplying Polynomials
This site gives practice multiplying polynomials.
http://faculty.stcc.edu/zee/newpage121.htm

Sonja Kovalesky
Did you notice the Historical Perspective at the beginning of this section? Sonja Kovalesky is one of the greatest women in mathematics history. If you want some additional information, you can check out this site.
http://www-history.mcs.st-and.ac.uk/~history/Mathematicians/Kovalevskaya.html