From Authentication Tools for Joomla! (JAuthTools)
The Remote Joomla plugin is a Joomla! 1.5+ plugin that uses XML-RPC to connect different Joomla! sites to each other and allow site to site logins.
It takes items in the following fashion: username@remotesite/path/tosite/
This will authenticate you as "username" at the remote site.
- Ability to limit authentication to trusted sites for both providing information (XML-RPC server) and user sources (Authentication plugin)
- Integration with SOAP SSO's provider list