Downgrade MacPorts Boost From Version 1.50.0 to 1.49.0
I recently upgraded to Mountain Lion and had some troubles with macports.
One specifically was that mongo no longer worked because boost was at 1.50. The fix is to downgrade to 1.49 however it's no longer an available port via the normal routine.
Here's a fix for that problem and will get you up and running with mongo again.