Students in the 4th grade will be following the Everyday Math series. I personally love the way Everyday Math (EM) is set up to help the students learn new concepts while practicing "old" ones. EM invites students to interact with the materials and includes games and opportunities for intervention.
The Everyday Math website has a lot of valuable tools and games for parents and students. Check it out!
Math Games are a great way to sharpen up on your math skills: www.coolmath-games.com
You can also check out IXL if you need additional help with ANY learning goal: www.ixl.com