http://keepass.info/
KeePass is a Windows password manager which focuses on strong encryption and secure passwords. It can run portably (with no install) from a usb disk or otherwise. There is a cross platform port called KeePassX.
http://www.keepassx.org/
KeePassX is a cross platform port of KeePass, a windows password manager. It focuses on strong encryption, secure passwords, and good practices. It runs on Windows / Mac / Linux, all portably (from a flash drive).