Homepage: http://www.mplayerosx.ch/
Issue tracker: https://github.com/sttz/MPlayer-OSX-Extended/issues
Downloads: http://code.google.com/p/mplayerosxext/downloads/list
The project can be built using either XCode 3 or 4. Make sure you've got the dependencies below and then you should be able to compile MPE directly with XCode.
MPE requires my Sparkle Fork. It adds updating separate bundles without a restart, used in MPE for updating its binary bundles with Sparkle.
It's best to use the same Fontconfig and Freetype versions as used in the binary bundle. The default setup links to the libraries inside the mpextended.mpBinaries bundle in the binaries folder. The easiest way to get that is download the latest (test) version of MPE and extracting the binary bundle form "MPlayer OSX Extened.app/Contents/Resources/Binaries".
Note: I've reorganized the bundle after the FFMpeg-MT merge and haven't released a test version with it yet. For now it's probably best to link to the system Fontconfig and Freetype libraries.
On Lion use the system's libiconv.2. On Snow Leopard the system's libiconv.2 is not new enough (Version 8 is required) so install libiconv using for example homebrew or macports, then link to it.