Sketch’s World, my personal favourite from the games available on multiplication.com, is now available for adding, subtracting, and division as well! Have fun practicing!
http://www.fun4thebrain.com/addition/sketchadd.html
http://www.fun4thebrain.com/subtraction/sketchsub.html
http://www.multiplication.com/games/play/sketchs-world
http://www.fun4thebrain.com/Division/sketchdiv.html
This is a game we found that the students LOVE! Structured like a video game, it challenges your basic fact knowledge in a really fun way!