Instant Sudoku Solver can solve any logical Sudoku puzzle instantly, meaning that it can solve all Sudoku puzzles that do not require some form of guessing. Soon I will have an updated version that can brute-force non-logical puzzles. This was written in 400 lines of AS2, and can generally solve puzzles in a tenth of a second.
To enter a puzzle, simply type in the numbers and press solve, or try out one of the presets.
If a puzzle you try does not entirely solve, then it requires some form of guessing or advanced logic to solve, and won't be solvable as of now.
UPDATE:Slight performance optimization, changed some of the code to accommodate future algorithms such as advanced logic and a brute-forcer.