Password Safe is an Open Source (free) tool that allows you to have a different password for all the different programs and websites that you deal with, without actually having to remember all those usernames and passwords.
Password Safe runs on PCs under Windows (95/98/NT/2000/XP). An older (but fully functional) version is available for PocketPC. Linux/Unix clones that use the same database format have also been written.
Download: http://sourceforge.net/projects/passwordsafe/