HoDoKu - HoDoKu is a sudoku helper written in Java and available in English and German.
Simple Sudoku - Freeware Sudoku Puzzle Maker and Solver
Yasminoku - Sudoku game and solver totally written in DHTML.
NumberDrop - A uniquely challenging math puzzle game.
USB Sudoku - A very small program for playing the original game of Sudoku.
nsudoku - A Sudoku game made with ncurses.