What to use to run a Sig?

My attempt to use Moodle to set up a web site for a Green Technology Sig for the ACS has not been entirely successful. Moodle was designed for courses and not surprisingly, force fitting a special interest group into the format of a course doesn't quite work. Any suggestions on what yto use (or if anyone has a Moodle add-on for Sigs), would be welcome.

Some suggestions I have had are Drupal, an open source content management platform. and Elgg an open source social networking platform.