Inspired by Max Berry's book, Jennifer Government, NationStates is one of the most popular online simulation games. The forum boasts over 5 million posts and 200,000 users.
Professional online broker and trading community.
Official Support Forum for Debian, the kernel-based open source operating system. phpBB provides a solid platform for support and discussion.
Support for Synology NAS devices and ideas for future versions of the DiskStation software.
KDE is mainly known for producing the KDE Desktop Environment (used in Kubuntu) for Linux.
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.