At Creative Contingencies we don't just use open source, we are also involved in the local open source community.
Our executive director was recently elected to be President of Linux users of Victoria. She lead the team that organised Linux Australia's linux.conf.au 2008 conference in Mel8ourne, and was a board member of Open Source Industry Australia from 2006-2008.
The CTO is the former secretary of Linux Users of Victoria and current Linux Australia secretary. He maintains a repository of 3rd party and custom-compiled packages, such as Google Earth and SecondLife for Ubuntu Linux, firmware files for Broadcom wireless controllers and development snapshots of Inkscape.
We contribute to documentation by maintaining wiki pages. When we find bugs, we try to send patches back to the software authors, thus increasing software quality for everyone.
We regularly attend meeting at our local Linux User Group - Linux Users of Victoria and the Drupal Melbourne user group. Check out our DrupalGive page, to see how we contribute back to the Drupal Project and Community.