If you're looking for a fun, interactive way for your child to practice and review math concepts, you may want to consider Mathletics. I had a trial membership for review purposes recently, and my daughter enjoyed it. The website is formatted somewhat like a social network, which is super-trendy right now, so the kids love it. (However, they don't actually communicate directly with other students, so it is a safe environment for kids.) Each student gets put together a personalized avatar, choosing skin color, hair color, hair style, shirt color, etc. Then, as they play the "games" (in reality, math drills) they accumulate points which they can use to further "jazz up" their profiles. That is a great goal incentive to keep them going back for more. They can also compete against other students around the world.
The parent gets a separate account and can log on any time to check the student's progress. That makes it handy to see how much they've done and what kind of scores they get on different types of problems.
Mathletics is designed for students in kindergarten through 8th grade. In addition to the online interactive games, there are also skill-specific workbooks you can print out. From what I could tell, it is meant to be a supplemental program, not a stand-alone math curriculum.
It costs $59 per student per year. (If you know the answer to the "human calculator's favorite number" (It's 9!) you can save $9.05 as the membership cost will only be $49.95.) They also offer a 10 day money back guarantee. Read other reviews on the TOS Crew blog.