http://www.purplemath.com/modules/index.htm
http://www.math.com/homeworkhelp/PreAlgebra.html
http://www.algebra.com/pre-algebra.mpl
http://www.gomath.com/algebra.html
http://www.classzone.com/books/pre_alg/
http://education.yahoo.com/homework_help/math_help/prealgebra
