Good practice of arithmetic with games that are actually pretty fun. The best part is that kids can play against each other (creating a game that others can join) if they want to. Good for add/subtract/multiply/divide/integers.
It only goes up to grade 6, however, some of the games apply. On the left hand side, there is a link titled "LINKS"...click on that for a million other websites for cool math games!
You can create a PDF of graph paper with this site. The default settings are usually good enough, but you may want to play around with the settings to create something else.