After just a brief exposure it’s already clear to me that Sodoku (and the web version in particular) is incredibly addictive. I spent a good portion of my lunch break playing and trying to improve my solving speed. I’m getting a better feel for it, but I’m sadly still far below average.
Wikipedia has a nice article on Sudoku with plenty of background and further information.
Update: It’s pretty sad that I mispelled sudoku as “soduku” and just realized it. Oops.