Asterisk is an open source IP PBX system (translation: it uses the Internet to make phone calls, using your own server -- this is usually called "Voice over IP", or VoIP).
The main news site for the Asterisk community just switched to using Drupal as their content management system. The big difference is now that they have such a flexible system in place, they're inviting their members to submit content:
The new Asterisk web site is powered by the Drupal content management system. The Asterisk community is being encouraged to create and submit content to be included on the web site. To submit content, just create an account. Once the account has been created and you have successfully logged in, you will be presented with options along the right which can be used to submit additions or changes to the web site.
So that's a pretty common announcement these days. Lots of sites, especially ones that tie into community in some way, are choosing Drupal. The great stuff comes from the release of an Asterisk integration module directly on Drupal.org:
Users can provide a phone number in their profile. Then users can click the 'call user' link to be connected automatically to another user.
It is a distributed system. The asterisk part communicates with drupal via xmlrpc. Therefore, the drupal site can be on a regular webserver while your computer at home or in the office (with asterisk installed and configured) completes the calls.
The module also provides an API, meaning that other features could be built into the Drupal system, relying on this extend the base functionality. All I can think is wow -- telephony integration is a very big deal, and I can't even begin to imagine the many creative ways this could be used.