Dinah made up a holiday called Discardia. She wrote:
I've decided to invent a new holiday called Discardia. It takes place in the time between the Solstices & Equinoxes and their following new moons. Discardia is celebrated by getting rid of stuff and ideas and habits you no longer need. On the Discardian new moon you don't buy anything or bring anything into your home and enjoy the fact that you have enough.
I think this is a fine idea. Dinah listed the upcoming ones, but I was on a hacking binge and thought it'd be fun to write some code to do it automatically. Mixing solar and lunar events gives it a peculiar schedule, but that just makes it more fun.
For up-to-the-second calculations, you can run it yourself (and notice the hackable URL), but for the less demanding, here are the 10 next upcoming Discardia (as computed on 11 Jul 2013):
Feel free to gawk at the code. It's written in Emacs lisp because Emacs has excellent calendar libraries that know about equinoxes/solstices and phases of the moon. I'll bet there aren't many dynamic web pages that use XEmacs on the back end.