In the resource room, we use an alternative program called Moving with Math. Please view the website. Specifically be sure to look at the problem solving link.
Here are a few of our favorite sites:
Operations and Algebraic Thinking
Great Math Site - interactive manupulative-based activities!!
Tic Tac Toe Squares - basic math facts (add., subt., mult., & div.) Also you can practice square roots.
Cool Math - timed practice, fun games, models of alternative math algorithms - All skill levels.
FunBrain.com - Try Math Arade on this site to practice math skills - All skill levels.