A paper notebook can be a perfectly good tool for managing computer passwords. It requires no power to use. It can be safely locked up. It's inexpensive and easy to use. But for various reasons, many admins don't care for this approach. If you prefer to use a computer to manage your passwords, take a look at Password Gorilla. Password Gorilla is a personal password manager that runs on Linux, Mac OS X, Windows, and just about any Unix.
Starting up Password Gorilla for the first time is bit tricky. You'll get a window asking you which password database to open. Hit Cancel, because you haven't created one yet. Go to the main window and click on File -> New. Now, you can create a new password database and give it a master password. Pick a safe place to keep your master password it will not do any good to keep it in Password Gorilla. Also, if you lose this password, you lose everything; there is no way to recover it.
Take a look at the various preferences and configuration options and season to taste. A good option to enable is "Auto-save database immediately when changed." You may also set your own password policies, such as length and permitted characters. Logins can organized into groups.
Password Gorilla can be used to store any and all logins and passwords. Retrieve them by either sending them to the Clipboard or having Password Gorilla enter them automatically into Web forms. We recommend using the Export feature to print out a hard copy for backup. This creates a plain text file, which obviously should not be on your computer.
Password Gorilla is both free of cost and Free Software. It is licensed under the GPL.