Atwww.thetapuzzles.com, there are some interesting three dimensional sudoku-like puzzles. They are named after the geometric form and difficulty. For example, cubicon is a cube and it is difficult, while octithin is an octahedron and is easy.
Really nice idea and interesting puzzle. I really like tredokus, and I only miss to play on line, cause I have no printer. That's one of the advantages for the link I sent, you can play on line. It's amazing how variated sudoku-like puzzles has become.