A UBB-style discussion board written in PHP. It includes many messaging features, private forums, and robust themes.
Monitorix is a free, open source, lightweight system monitoring tool designed to monitor as many services and system resources as possible.
SABnzbd Plus is a free/open-source cross-platform binary newsreader written in Python.
Usermin is a web-based interface for webmail, password changing, mail filters, fetchmail and much more.
Sonarr is a PVR for Usenet and BitTorrent users. It can monitor multiple RSS feeds for new episodes of your favorite shows and will grab, sort and rename them.
Wacko Wiki is a light and handy Wiki-engine.