If you want not just to play sudoku but to also learn hot tips and increase your skill, i recommend http://www.printablesudokuonline.com. It has 5 very easy sudoku puzzles per day, 5 easy sudoku puzzles per day, 4 hard sudoku puzzles per day, 1 very hard sudoku puzzle per day and access to the e-book “Secrets to Solving Sudoku Puzzles”!

Enjoy!