HoDoKu - HoDoKu is a sudoku helper written in Java and available in English and German.
Yasminoku - Sudoku game and solver totally written in DHTML.
Simple Sudoku - Freeware Sudoku Puzzle Maker and Solver
NumberDrop - A uniquely challenging math puzzle game.
nsudoku - A Sudoku game made with ncurses.
Planet Sudoku - Play millions of free Sudoku puzzles online for kids to experts. Sudoku puzzles like 9x9, Samurai, 4x4, 6x6, 8x8, 12x12, 16x16, 20x20 and 25x25.