Figured someone else would beat me to it, but even so now it's out there.

I always this bit of "Pinky and the Brain" on this day: http://www.youtube.com/watch?v=S7pNAddsQk8

I've heard the "hip" thing is to now call is Half-Tau Day.

Tau is often used to represent 2pi

But yes, Happy Pi Day indeed!

Call me un-hip then.