Map any blog/site on a WordPressMU or WordPress 3.X network to an external domain.
This needs patches to stop it from triggering errors. No longer developed as far as I can see.
Find the latest version (which is not this one!)
Additionally I have a spurious redirect loop happing on two of my domains. Switching to Mercator by humanmade fixed it, although that plugin currently immature and has issues of its own.