It's not that easy...
...And I'm not disclosing the solution.
What I'll do is give a year's pro membership to the first person who makes these, solves the puzzle and adds a photo of the finished pyramid in the comments below to prove it.
The stl file is for 6 sets. The pieces are small, will fit into your pocket and allow you to take them with you to hand out. If anyone wants a single piece, let me know and I'll publish the file for a single piece.
Trust me, you'll want a lot of them. They make great hand-outs.
Update - June 22, 2012:
New Pro Member Mathlas has won this contest using "old" technology. He posted a photo that looked so much like it was computer generated, I had to make sure he really made it. Sorry for the delay, Mathlas and congratulations.
Update - July 18, 2012
It's been a month since the contest and time for me to explain the difficulty behind this puzzle... First, there's a mild optical illusion going on with the rectangular part of the shapes. The square looks a tiny bit longer in one direction. your subconscious, like your boss, will tell you that rectangles only fit together in one direction, but won't tell you why.
Next, and this is more diabolical: when asked to make a pyramid, everyone will think of an Egyptian pyramid. Egyptian pyramids have 5 sides... 4 triangular and one square (the bottom), This pyramid, is a true pyramid with only 4 sides,,, All of them triangular. It's very difficult trying to solve a puzzle when your blueprint is of something else.
And thanks to everyone else who replied. I'm going to be busy sending off badges for quite a while :)
And while you're voting for me, why not check out all of my other Instructables using my own Chindogu SMARTPHONE APP (It's free, kinda cool... But, clearly worthless. Ya gotta check it out at http://app.cat/bfksinstructables/