KDE is mainly known for producing the KDE Desktop Environment (used in Kubuntu) for Linux.
Pixelmator is a popular commercial image editing software for Mac OS X users.
Avant Browser is a fast and user friendly browser which uses Microsoft's Trident rendering engine. The browser has been downloaded over 22 million times.
Discussion board for the massively popular xkcd web comic. Covering everything from Maths and Science to Logic Puzzles and Forum Games. Over 100k members and 2.4 Million posts.
The VideoLAN project produces the extremely popular VLC media player software. Their forums provide support for users of the software as well as the development community.
VirtualBox, developed by Oracle, is cross-platform x86 virtualisation software. It has become one of the most widely used virtualisation solutions in the world.