SitePass

This extension generates a unique password for each different site you wish to use. The password is generated by one-way hashing a combination of the website's domain name (you can override this) and a secret password you enter yourself. If you always enter the same password, you'll always get the same SitePass for a given domain (on any machine)

Thus you can have a different password for each website without having to store them in one place.

All password activities are done locally in the extension; nothing is sent over the network.

Future versions will support more than just 8-hex-character passwords.