PythonTheater is a multimedia player capable of AVI/ASF/WMV/MPEG-1 and VCD playback. It can make use of the XVideo extension where available to provide fast playback and smooth scaling. It also supports features such as drag and drop from Nautilus, gmc, konqueror, rox, and others.
Freevo is a Linux application that turns a PC with a TV capture card and/or TV-out into a standalone multimedia jukebox/VCR/PVR/HTPC/DVR/set-top box. It uses MPlayer and other applications to play and record audio and video. It is optimized for use with a TV and remote, but can be used with a monitor and keyboard.
LiVES is a simple to use yet powerful video effects, editing, conversion, and playback system aimed at the digital video artist and VJ. It runs under Linux, BSD, Mac OS X/Darwin, IRIX, and openMosix. It is frame and sample accurate, can handle almost all types of video, and is fully extendable through plugins and the included plugin builder tool. It can also be controlled remotely using OSC.
KatchTV is an "Internet TV" application for KDE. It makes it easy to subscribe to "TV" channels from all over the Internet in the form of podcasts, so that you can browse channels, download shows, and watch them, all from one convenient interface. It is very similar to Democracy TV, but focuses on KDE integration, using KHTMLPart and embedded players such as kaffeine. It's much faster and lighter on resources if you run a KDE desktop without GTK apps. Installation is easy as long as your distribution has PyKDE and PyQt.