Sudoku Susser is a comprehensive Sudoku assistant and master-level solver.

Hints mode shows you what numbers are legal for the remaining squares. The Deducer uses human-style reasoning to solve the puzzles and can take you step-by-step through their solution with detailed explanations of each step. The brute-force Recurse option solves all puzzles. And tons of hilighting modes help you see the patterns in the puzzles.

You can even drag puzzles right off the web-pages of major UK newspapers into the application, then edit, save and print them for offline fun.