Games:
http://www.math-play.com/math-racing-place-value-game/math-racing-place-value-game.html
http://www.abcya.com/place_value_hockey.htm
Prime/Composite Games:
http://www.sheppardsoftware.com/mathgames/numbers/fruit_shoot_prime.htm
http://www.abcya.com/number_ninja_factors.htm