KDE is mainly known for producing the KDE Desktop Environment (used in Kubuntu) for Linux.
Solia Online is one of the most active online communities with over 18 million posts. Solia Online allows you to create your own avatar, buy items, and discuss topics with your friends.
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.
Discussion forum for the massively popular American animated sitcom. Powered by phpBB.
OpenOffice.org offers a free and fully-featured office suite which meets the needs of the common consumer all the way up to large enterprises.
It is the Italian Community for Ubuntu, a popular open source community operating system based upon the the Debian Linux Distribution.