These are the two websites that I go to in order to get puzzles:|
They have 4 levels of puzzle. websudoku.com has Easy, Medium, Hard, and Tough. sudoku.com.au has Easy, Medium, Hard, and Evil. I no longer do Easy or Medium, since they are too easy. Some Hard puzzles are very easy, and some are very hard. I rarely can do the Tough puzzles on websudoku.com with making guesses for certain squares, but I can regularly complete the Evil puzzles on sudoku.com.au.