I’d nearly forgotten all about this game, Sudoku, until I saw Joe Grossberg blog about one that’s freely available to play on the web at www.websudoku.com. The screenshot to the right shows the result of my lunch hour, today.
Update: If you’re looking for another online place to play, check out Iron Sudoku, where a new puzzle is posted daily and you can chat in realtime with other people who are playing the same puzzle. It’s very nicely done, although the interface might be a little awkward at first, you do get used to it and it’s very playable.
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Programmer, husband, father, singer, guitarist, tinkerer, reverse engineer, strange, and living in New Jersey. 
Thanks for the sudoku links! I found this site really helpful when I was learning how to play sudoku. I’m not sure if you’re interested in watching how to videos, but these are great for beginners.
Very good implementation of Sudoku: Sudoku Arena.
This multimedia Sudoku puzzle is unique in 3 ways. Level of difficulty is based on 5 parameters which gives very precise puzzles. Theme graphics, music and sounds create a great atmosphere. Drag & drop playback interface makes playing more intuitive. Many helpful options are available, especially for Sudoku beginners.