On the night of December 23rd, 2007, the full moon will occult Mars. This is unusual in that Mars will also be near its opposition, where it appears the largest in the sky. Its not very often that a full moon occults a planet at its opposition, so this will be an event to catch!
Observers in the Northwestern US are most likely to see the event. Unfortunately, the event may not be visible at all at my location, but I will definitely be watching, assuming skies are clear.