Account Sync

The account_sync module allows you to synchronize drupal user account data across
multiple Drupal sites. It currently supports basic account information as well as the drupal core profile module. It also has very basic single sign-on support.

This module uses XMLRPC to transmit data between sites when updates are made so
there's no need to have your sites running on the same database, server, or on the
same subdomain.

If you plan on using this module please read the README.txt. If it's not configured properly you can risk breaking your user accounts and opening security holes.

You may also be interested in the Bakery module which has similar functionality and goals. I've added a short document explaining some of the biggest differences between the two modules.

If you're curious about some of the possible use cases of this module, check out USES.txt