Check this out!

 http://www.coolmath-games.com/

This is a "cool" site for students to use in their spare time! This site has many games that students must use math skills to play. In the classroom, I would use this website for when students finish work early in the classroom. This way students are still learning but they are having fun, and they are engaged! Students will have fun with this website and will not even realize they are learning.