Sudoku Explainer
Sudoku Explainer Java (Swing) GUI explains how to solve Sudokus
Keith Corlett's open-source Sudoku Explainer explains ANY Sudoku puzzle, and generates human puzzles. It's a Java (Swing) GUI based on DIUF Sudoku Explainer by Nicolas Juillerat (rewritten for speed) with all hinters from HoDoKu by Bernhard Hobiger, plus a few from sudopedia.com.
SE explains a simplest possible solution to ANY Sudoku puzzle. It's pretty fast. It generates basic (human solvable) Sudoku puzzles, but takes ages to generate difficult Sudokus. It cannot, except by chance...