THE place to find sumo games on the Internet is: www.sumogames.com

There are 23 various games that can be played Before, During, or After each Basho.
 

There’s also a few sumo games/puzzles on the Internet you can play:

Keyboard Sumo: http://www.chthonic.f9.co.uk/sumo/

Kimarite Puzzle: http://www.geocities.com/cfinberg862/kimarite.html

Sumo Big Puzzle: http://www.geocities.com/cfinberg862/SumoBigPuzzle.html