I Roll 20's

http://www.makerbot.com/blog/2011/09/29/openscad-challenge-regular-icosahedron/

It didn't take me too many lines of code, but I did use two libraries so make of it what you will. ;)

BTW, just because it's OpenSCAD code, don't assume it's 100% parametric. It's pretty close though, someone just needs to come around and iron out the formulas.

Uses:
WilliamAAdams's Platonic Solids: http://www.thingiverse.com/thing:10725
Tony Buser's Bitmap module: http://www.thingiverse.com/thing:2054