Ophcrack is a free rainbow-table based cracker for Windows passwords (though the tool itself runs on Linux, Windows, and Mac). Features include LM and NTLM hash cracking, a GUI, the ability to load hashes from encrypted SAM recovered from a Windows partition, and a Live CD version. Some tables are provided as a free download but larger ones have to be bought from Objectif Sécurité.
For downloads and more information,
visit the ophcrack homepage.
Excellent tool for passoword discovery, you can download the free version which comes with small rainbow table that will discover most "simple" alphanumeric passwords, for complex password you might want to purchase additional rainbow tables. You can also download the iso file and burn it onto a cd or usb. All in all is a great tool!