I have finally got around to registering the Addressbook plugin on wordpress.org. From now on, I will use the Subversion repository there for managing the plugin, and not this site; I will still post update announcements here, though.
See wordpress.org/extend/plugins/addressbook for the latest version and other information. The version that I have just put up there is 0.4, the same as the latest available here; I will be incorporating people’s suggestions, and releasing a new version — maybe even 1.0! — soon.