http://www.ixl.com/math/algebra-1 (once you are one the site select the objective we are working on to get several practice problems)
http://www.aaamath.com (for extra practice in Pre-Algebra skills)
http://www.hippocampus.org/?select-textbook=2 (for Algebra I)
http://www.uiowa.edu/~examserv/mathmatters/ (math matters at Iowa - gives math courses needed and practice final exams)
http://feromax.com/cgi-bin/ProveIt.pl (two column proof practice)
http://feromax.com/cgi-bin/ProveIt2010.pl