These were all rendered using SketchUp and printed at Shapeways. The helmets all fit on lego or kreon style heads (there's even a little peg hole in the center to keep them nice and snug).
"And I will have a hat party, with my chapeau being the grandest of all!"
"...cross me, and you'll soon discover that under this playful, boyish exterior beats the heart of a ruthless, sadistic maniac."
-Lord Edmund Blackadder II