Mount Vernon News Unlimited puzzles with a choice of Easy, Medium or Hard.
Mousebreaker Loads of diffrent types of sudoku games to play online.
Puzzle Choice Choice of online or printable puzzles.
Said What Online games to play and an e-book to buy.
DKM Software
Online games with a new puzzle generated every time you want to play. There are also some great card games to play too.
Paul's Pages Website from Computor Journalist Paul Stevens includes Random Sudoku - The game is randomly selected and may be easy, an 'absolute mind-boggler' or anything in between. It can also be used as a solver.
Web Sudoku
Three games to play online, one each of easy, medium and hard.