I created a new screencast today, demonstrating that you can tessellate any shape that has either three or four sides (a.k.a. triangles and quadrilaterals). At the end of the video, you'll also see some cool patterns you can make using irregular pentagons and hexagons.
I'll be presenting some of this stuff to a room full of math teachers tomorrow at the Annual Meeting of National Conference of Teachers of Mathematics (or NCTM). SketchUp is a fabulous tool for teaching 2D and 3D geometry in school, but not nearly enough educators know about it.
The projects from this video are detailed in two of my GeomeTricks books:
Anyone can design anything in 3D! www.3dvinci.net