I recently read about a website called Sumdog. It's a free website with highly engaging games for practicing math. It covers a dizzying range of topics from basic number concepts to exponents. Basically, the games can be played for any skill. If you look at the picture below, you see all the skills for multiplication. Players choose a skill and then choose one of the games. The game randomly matches a player up with other online players or the computer to add another level of competition. You can see by the 2nd and 3rd pictures that I was practicing making doubles using two different games.
While the games are free, there is a parent subscription available that provides additional functionality. With a subscription, parents can view reports and set up challenges for their children. Their children can also set up games with other Sumdog members instead of playing against random players. You actually have to sign up for a parent account to get information on pricing, but it looks to me like it is $6 a month.
This is a great resource for making math practice fun! I hope you'll check it out. If you're already using Sumdog, be sure to leave a comment and let us know your favorite features.