Yesterday evening on All Things Considered, they shattered the idea that tonight's full moon is a blue moon. The next blue moon will be in May 2008- the third full moon in a season that contains four.
See, we all thought that a "blue" moon was the second full moon in a calendar month, something that only happens rather rarely. This is a mistake, perpetuated by a Sky and Telescope article over sixty years ago. Give the NPR article a listen to hear the details.