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.
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.