ClassTools.net is easily one of my favorite sites. It gives teachers and students the ability to "create free games, quizzes, activities, and diagrams". This site is free and very easy to use.
Some of my favorite tools on this site:
Fakebook and Twister - create fake Facebook and Twitter posts. Great to use for historical or fictional characters.
Random name Picker - just as it describes
Countdown timer - you can add a tune or YouTube video to your timer.
Venn Diagram Template
And the newest game creator, Pac-Man. This is a great review game creator. Make sure to use the help section to learn how to enter questions and answers. Students answer questions and continue to play Pac-Man until they get a question incorrect.