If you have already decrypted passwords for Firefox 1, 2 and 3 (if you need them, it’s here), here is the source code in C that helps you decrypt Firefox passwords for version 3.5 and 3.6! This source code is written by ZeR0 from HackHound.org. This source code is generally open source by the author but the terms of use is to give credits if you use it.
Download source code here (link removed).
Download binary / application here (link removed).