Math Games: Volume!

http://www.coolmath-games.com/0-countcubes/
http://www.xpmath.com/forums/arcade.php?do=play&gameid=118
http://www.mathplayground.com/cube_perspective.html
http://pbskids.org/cyberchase/math-games/can-you-fill-it/
http://www.math-play.com/geometric-figures-game/geometric-figures-game.html