You can try Sudoku grids of different difficulty level now!
Very Easy
Easy
Medium
Hard
Expert
Click on the links below to try ONLINE Sudoku:
http://www.dailysudoku.com/sudoku/index.shtml
If you are interested in trying the Killer Sudoku, which is really challenging, you may visit this site:
http://www.killersudokuonline.com/play.html