You may download a Windows version of Numbler which gives a number of additional features which are not available in the online version.  You may print Sudoku puzzles with 2, 3 or 6 to a page.  You can have multiple storage containers of puzzles and organise those puzzles within them.  You can use it to solve Samurai Sudoku - 5 overlapping Sudokus or Kakuro puzzles.  Here are a few screen images: