According to an article on the Cincinnati Enquirer today (http://www.enquirer.com/editions/2004/07/31/loc_b luemoon31.html)
"Only once in a blue moon is there controversy over exactly what constitutes a blue moon. But it's not a blue moon in the strict definition of the 19th Century Farmer's Almanac. According to the almanac, a true blue moon is the third full moon in a season that has four full moons. This also happens about every three years, but on a different cycle from the blue moon that occurs tonight. Confused? So is the American Heritage Dictionary, which lists both definitions of the blue moon."
Slashdot Mirror
According to an article on the Cincinnati Enquirer today (http://www.enquirer.com/editions/2004/07/31/loc_b luemoon31.html)
"Only once in a blue moon is there controversy over exactly what constitutes a blue moon. But it's not a blue moon in the strict definition of the 19th Century Farmer's Almanac. According to the almanac, a true blue moon is the third full moon in a season that has four full moons. This also happens about every three years, but on a different cycle from the blue moon that occurs tonight. Confused? So is the American Heritage Dictionary, which lists both definitions of the blue moon."
More in the article. Interesting Stuff