It seems that Alex his MultiWiiCopter is booming!
Rumors go that the MultiWii Multicopters are the most widely known & spread multi copters in the world.
I don't know if it's true but fore sure Alex his project evolved tremendously in the past year!
Main links & info:
The main website of the owner of the MultiWii project is www.multiwii.com.
The (huge) main RC groups thread where all discussions are held can be found here.
Kinderkram & Blue Angel have made excellent build logs! They are available here and here.
Another very good post for initial set-up and basic questions from Shikra can be found here.
The source code can be found on the Google code repository here.
I strongly encourage to read Alex his website & Kinderkram's or Blue Angel's build logs, they contain normally all information needed to build the MultiWii.