As a reluctant sci-fi geek, I feel compelled to mention that today is what is often acknowledged as "Star Wars Day" or "Luke Skywalker Day." I must mention it if for nothing other than the fact that my older brother and I would spend days in the summer watching all three movies in a row and eating Spaghettios out of the can when I was about seven. Ah, childhood.
Today is the May the 4th which makes a clever little pun "May the fourth be with you."
Though according to Wikipedia, attempts to create a Jedi church have failed and no group other than hardcore Star Wars fans celebrates the holiday, it is still a pop culture mini-phenomenon.
In Los Angeles the city council declared May 25th Star Wars Day (the 25th was the release date of A New Hope back in '77). However, the 25th is also known as "Geek Pride Day" and "Towel Day".
Though I can't speculate what special activities one would do on Geek Pride Day, fans of Douglas Adams carry towels around on Towel Day.