Here is an updated list of useful security auditing extensions :
Whois and geo-location
ShowIP : Show the IP address of the current page in the status bar. It also allows querying custom services by IP (right mouse button) and Hostname (left mouse button), like whois, netcraft.
Shazou : The product called Shazou (pronounced Shazoo it is Japanese for mapping) enables the user with one-click to map and geo-locate any website they are currently viewing.
HostIP.info Geolocation : Displays Geolocation information for a website using hostip.info data. Works with all versions of Firefox.
Active Whois : Starting Active Whois to get details about any Web site owner and its host server.
Bibirmer Toolbar : An all-in-one extension. But auditors need to play with the toolbox. It includes ( WhoIs, DNS Report, Geolocation , Traceroute , Ping ). Very useful for information gathering phase