MMS (My Media System) is a is an open source media center application for Linux. With MMS you can playback videos, brows digital photos, listen to music, or even get the local weather report. Best of all, you can run all this with a remote control.

mms running on a 22 inch monitor

Other media center software for Linux
Over the years I have used MythTV as my media center software, and even dabbled a bit in Elisa. Also Sofa Media Center looks promising, but without lirc support it's not in usable state yet.

Advantages MMS has over MythTV and Elisa:

MMS is easier to configure than MythTV. Even if you have to compile MMS from source, I have found setting it up to be less work. There is no fussing around with mysql passwords, or seemingly endless configuration screens. I don't mean to bash MythTV, but if you just need a video jukebox MMS is a lot more expedient.

Automatic thumbnailing of videos in list view. In MMS when you select a video from your library you get a thumbnail preview of a scene in that video. It's a very simple feature, but it's essential if you have a large collection of video files. Elisa will do this too, but MythTV does not.

Can use Mplayer for video playback. Unlike Elisa, MMS can be easily configured to use Mplayer as the video playback application. That's important because .wmv files are all to prevalent, and gstreamer based video players and even VLC don't do very well with them. Note I have not tested .wmv with Fluendo's paid GStreamer codec plugins - so I am not saying this is true all the time.

Installing MMS:

I'll do a post shortly on how to compile MMS on Ubuntu, but if you are just itching to get started you will find some .debs one of the developers put together in their forum. Also I wrote up some compilng instructions and posted them in their wiki.