Gentoo Linux is an open source operating system built on top of the Linux kernel and based on the Portage package management system.
As the official board for the world-famous band Queen, this community hosts a wide variety of discussions by Queen fans from around the globe.
OpenCart is popular, powerful, and easy to use shopping cart software. Their healthy community forums are powered by phpBB.
Hugely popular Mozilla community providing support for Firefox, Thunderbird, Seamonkey and other well known Mozilla products. Over 350k members and 4 Million posts.
Support for Synology NAS devices and ideas for future versions of the DiskStation software.
Pixelmator is a popular commercial image editing software for Mac OS X users.