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
nsudoku - A Sudoku game made with ncurses.
Get Sudoku - Get Sudoku is an interactive sudoku solver.
NumberDrop - A uniquely challenging math puzzle game.