I'm planning a Blue Moon Party for May 31, 2007. It's the first Blue moon in three years. I'll celebrate the Blue Moon, even though sticklers for historical accuracy won't call it a Blue Moon. I'm thinking of making Blue Moon and star cookies, and a Blue Moon punch. Everyone who has ever used the expression 'once in a blue moon' is invited to my little event, which will be held here at vegetarian bear. For entertainment, we'll watch everything happen that people said would occur 'once in a blue moon', since the last blue moon (three years ago).
The Blue Moon is the patron of pandas, because bears (except pandas) are not vegetarians, and the moon is not normally blue. For those who live in the Eastern Hemisphere, the moon will not be blue until June 1, so it's not rude if you arrive late to my party.
The next time that a full moon occurs twice in the same calendar month will be December 31, 2009, (you don't suppose Blue Moon Party invitations grow on trees, do you?).
I don't plan to throw a party for the older (original) blue moon, which doesn't happen again until May 2008, and is defined and calculated by a formula explained here.
My serendipity into blue moons began with a moon phase analog at SAHW's blog.
I followed a link, and some links later, ended up downloading QuickPhase, a visual analog of moon phases past, present and future. It's an amazing tool for accuracy with time lines and descriptions, potentially useful with software like yWriter2, which allows a writer to track the virtual time elapsed in a scene or a book.