How to make Firefox use the Gnome Keyring vault for password storage and retrieval?
Solution 1:
There was an extension in AMO site, but it seems it has been removed. You can get the source code tho, from https://github.com/mdlavin/firefox-gnome-keyring
I haven't used this for a while and I don't know about it's security, so use it at your own risk.
Solution 2:
The working firefox 4+ extension is found here: http://www.webupd8.org/2011/06/save-firefox-passwords-in-gnome-keyring.html
It is not yet perfect, but works.