Here's 3 things to check while waiting for that 3 Sum:

To Play:
Threes Online Trivia Quiz
3Quiz

To Learn:
List of Threes in Anatomy (Pixies might want to check the Pelvis and Perineum section )
Anatomy3s

To Contribute:
You can add to "The Book of Threes" (Once there, click on PARTICIPATE)
Contribute3