It's Pi Day, which means it's the 2nd blogiversary of Grey Matters! Grey Matters has come a long way in those two years, and it's still growing.

To kick off the celebration, there are many changes over at Grey Matters Online Store. Do you want to learn and remember 400 Digits of Pi? Then you'll appreciate the new and permanent $10 drop in price for my memory course, Train Your Brain and Entertain! Yes, it is now only $29.95, which also applies to the downloadable version at Lybrary.com, too.

Maybe you've remembered the digits, and just need a way to show off your knowledge. In that case, you can wear Pi. The prices on all the T-shirts on the site have been reduced, so if you've been hesitating purchasing a shirt, check out the new lower prices!

Speaking of the Pi designs, I've added a shirt with the Pi Chart on the front, in both women's and men's clothes, in response to numerous requests.

For that matter, what is Pi good for? Well, it's central to the new Pizza Theorem section, for one. I first mentioned the Pizza Theorem earlier this month.

Need some help celebrating Pi Day? Start with PiDay.org, and then move on to TeachPi.org and Pi Nation! If it helps you learn, you can even sing about Pi (Flash required). Naturally, there's plenty of Pi to go around both on the Grey Matters Blog and Grey Matters Videos.

Before I go, let's not forget that it is the 128th anniversary of Einstein's birth today.

Have a happy and fun Pi Day!