Online Multiplayer Sudoku

Tired of playing Sudoku alone? Try Sudoku Combat, an Ajax multiplayer Sudoku gaming site. Now you can challenge a friend, or a complete stranger to a game of Sudoku. There are different skill levels to choose from, so you can be matched up accordingly.

This site is very nicely done!

What’s a Sudoku?

Sudoku (??, su-doku?), also known as Number Place, is a logic-based placement puzzle. Completing the puzzle requires patience and logical ability. Although the puzzle was first published in a French newspaper in 1895, it underwent a revival in Japan in 1986 and attained international popularity in 2005.

For more information on Sudoku, see its Wikipedia entry