3.14159265358979323846264338327950288419716939937510582097494459230781640628...

...you know the rest. It's Pi. It's great. And now you can work on remembering to rest of it with 'Digits of Pi' an educational app for Windows Phone 7. It supports the first 100,000 digits of Pi, so have a try.
The premise of this app I have created is simple, you just enter the digits of pi and everything goes along smoothly until you enter a wrong digit. At that point the number you selected turns red and the number you should have chosen turns green.