Universal Media Server is a DLNA-compliant UPnP Media Server, which is implemented in Java and thus runs on all operating systems. It can convert any media file format, and stream it to a wide range of hardware devices (smart TVs, and media centers).
Kodi spawned from the love of media. It is an entertainment hub that brings all your digital media together into a beautiful and user friendly package. It is 100% free and open source, very customisable and runs on a wide variety of devices. It is supported by a dedicated team of volunteers and a huge community.
Parole is the video and media player for the XFCE4 desktop. It has a simple and unobtrusive interface, utilizes GStreamer for maximum audio/video format coverage, and requires few resources. It provides a couple of plugins however, such as notifications and systray integration or remote control support.
CXine is a mostly mplayer-compatible keyboard driven X11 media player built on libxine and having support for embedding in other windows/apps; sticky, stayontop, fullscreen and shaded windows; keygrabs; bookmarking current playback position; user definable on-screen displays; downloading using external helper apps; streaming media and more.
PlayShell is a simple console-based application for playing media files in Linux using known media players like SoX, VLC, MPlayer and FFplay as backend.
The RedMatrix (aka "red") is an open source webapp providing a complete decentralised publishing, sharing, and communications system. It combines communications (private messaging, chat and social networking), and media management (photos, events, files, web pages, shareable apps) with enough features to make your head spin. What makes the RedMatrix unique is what we call "magic authentication" - which is based on our groundbreaking work in decentralised identity services. This ties all RedMa
FileBot can automatically rename tv show / movie files, and download subtitles. It requires little work, as media files can just be drag'n'dropped in for operation. It's cross-platform and comes with a command-line version.