ExploreMath is a great web site with all kinds of interactive activities that cover from elementary algebra through pre-calculus. Created by a math teacher, it has rounded up all sorts of math games, puzzles, practice sites, etc. Please drop by for a visit. Mrs. Glosser's Math Goodies is a free web site offering all kinds of activities and resources. House of Math Stories is exactly what it sounds like-math reading problems sorted by topic and difficulty levels.
Permission is granted for teachers to print worksheets.
ARC is a web-site designed for Algebra I teachers and students across the Commonwealth. Their emphasis is on locating and cataloging web-based information that can be used to enrich and reinforce the curriculum, while also helping to make algebra fun and relevant. Math is a great site, offering pre-made flashcards, online practice, and printable worksheets. It also includes a gameroom and homework helper. Very helpful, and fun.