Here's a set of puzzles I've been working through lately. It's a free download from sudoku-magazine.com.
https://qjy3pw.blu.livefilestore.com/y1 ... oad&psid=1It contains a good variety of different sudoku puzzle types:
Classic Sudoku
Sudoku X
Jigsaw Sudoku
Jigsaw Sudoku X
Windoku
Sohei Sudoku
Samurai Sudoku
Argyle Sudoku
Consecutive Sudoku
Even-Odd Sudoku
Flower Sudoku
Butterfly Sudoku
Windmill Sudoku
Twin Sudoku
I've completed all of the classics and a couple of the jigsaws. I found I wasn't able to do the Sudoku X without pencil marks.