Easy
http://www.sheppardsoftware.com/USA_Geography/USA_G0_click_1024.html
Medium
http://www.sheppardsoftware.com/USA_Geography/USA_G1_1024_768.html
http://www.sporcle.com/games/g/stateabbreviations
Hard!
http://www.sporcle.com/games/g/states
And...if you get tired of the US:
http://www.sporcle.com/games/g/japanprefectures
AND FOR YOUR CELL PHONE! Please download fromm apple store or google play.