At previous CDMUG meet-ups it has come up that many have been interested in a CiviCRM meet-up. Now there is one!
http://www.meetup.com/Chicago-CiviCRM/
As CiviCRM is cross-platform (it can also be deployed on Joomla! and soon Wordpress) the meet-up is not specifically Drupal-centric; but there's plenty of goodness to be had for Drupalers.