ff3sudoku is an add-on that features an engine for playing Sudoku puzzles. It can generate random puzzles, but it also detects and imports Sudokus from several Web sites, including websudoku.com, sudokupuzz.com, sudoku.com.au, and others. There is also a stand-alone version working in Firefox 3+ and GoogleChrome.
MAPDAV (More Accurate Password Dictionary Attack Vector) is designed to use what is known about users via the /etc/passwd file on Unix/Linux systems to generate a dynamic dictionary of more accurate guesses as to what their possible password may be. It does this by mangling the user's username and user information in various user-specified ways to look for bad password protection practices.