KDE is mainly known for producing the KDE Desktop Environment (used in Kubuntu) for Linux.
OpenCart is popular, powerful, and easy to use shopping cart software. Their healthy community forums are powered by phpBB.
Zend Technologies is one of the largest and most popular companies producing a wide variety of tools and frameworks for PHP. Their community forums rely on phpBB.
It is the Italian Community for Ubuntu, a popular open source community operating system based upon the the Debian Linux Distribution.
Professional online broker and trading community.
Pixelmator is a popular commercial image editing software for Mac OS X users.