In actuality, it's officially Pi Day (get it? 3.14? - No? I'll wait while you go get another coffee). Find out more via the official Pi Day website or check out my post from last year.
I still prefer ThinkGeek's approach. They combine Pi Day with Einstein's birthday under the banner of Pi-nstein Day. You can find out more on their site.
Happy Pi-nstein Day to you!
p.s. Don't forget to change your clocks. March 14th is also the start of Daylight Saving Time.