KeePass is pretty awesome:
1. FOSS
2. 'Unofficial' ports for Linux, Mac OS X, JME, iPhone, BlackBerry, PalmOS and Android
These are features on the Windows build so I'm not sure how many of these are available on the ports:
3. You can secure your passwords DB with a passphrase, keyfile or your Windows user account (I don't know why anyone would pick that one though, one reinstall and you're locked out)
4. Nifty features like automatically clearing the clipboard after a timeout, automatically locking the interface on certain triggers and auto-type (automatically type in the username and password into other windows, like a form on a webpage when you hit a key combo)
5. Auto-generation of strong passwords
It'll create an encrypted DB of your passwords which is stored as a file. So you can easily take it with you. I use Dropbox to sync mine across all my machines. And if you use a portable version on a USB stick, you can access your updated DB from any machine.