A new version of MAMEoX has just been released. You can find the changelog here.

MAMEoX is a port of the popular MAME (Multi Arcade Machine Emulator) system to the XBOX. The main goals of the project are to provide a well documented port with a consistent coding style.

Official Site: http://sourceforge.net/projects/mameox/
Download Sources: here (sourceforge.net)
Download Binaries: n/a (built with XDK)