KeePass: Password Safe
Here's an Open Source application this is even more multi-platform than usual.
KeePass:: The Open Source Password Safe
The original version was written for for use with Microsoft Windows. However, its author lists unofficial ports for Linux/Mac OS X (X11 required for the Mac), Palm OS, Pocket PC (Windows Mobile), and even the USB flash memory U3 portable smart technology format.
The application's official description reads: KeePass is a free/open-source password manager or safe which helps you to manage your passwords in a secure way. You can put all your passwords in one database, which is locked with one master key or a key-disk. So you only have to remember one single master password or insert the key-disk to unlock the whole database. The databases are encrypted using the best and most secure encryption algorithms currently known (AES and Twofish).
I have been using password
I have been using password managers for about 12 years (according to the date on my oldest entry), and I periodically review the current crop. I did so recently for my website, and arrived at KeePass as the best of the bunch.
I wrote on screencast on KeePass, which you can watch here:
http://mainstream-guides.com/keepass
Subsequent to making this
Subsequent to making this comment, I ran across another password manager that represents another approach. Called "PassPack," it keeps your passwords on a server, so you can access them from any browser, on any computer with a live internet connection. It encrypts and decrypts locally, so only encrypted information is sent over the wire. The server has no knowledge of your passphrases (two per account) or anything else about you, so it should be at least as secure as a local app like KeePass. Also, it has a 1-click logon to your password-protected sites, so it can be quite a timesaver.
At any rate, if you want to see my screencast on the PassPack alternative, it's here:
http://mainstream-guides.com/passpack