XBMC (Xbox)
From Wiki-Scene
Originally known as Xbox Media Player, the name was changed to XBox Media Center and then finally just XBMC (as it has since been ported to run on systems other then just the Xbox).
Perhaps the most popular Xbox dashboard amongst those who know of it, XBMC is certainly the largest to install - over 100mb (or potentially even more, as many extra skins/scripts/plugins can be installed). It is also the best maintained dashboard available, in fact development continues and fresh revisions are released to the project's SVN at an impressive rate.
Along with the provision of most of the standard dashboard features (such as a graphical file management system, the ability to run other programs stored on the console, http://xstretchmarks.com/stretch-mark-removal/ and settings pages dealing with other console attributes) XBMC also allows users to play just about any media file under the sun. Unfortunately the Xbox's stretch mark removal are inadequate for (most forms of) HD media however the software functionality is present nonetheless.
