3 links
Pick's Theorem
cut-the-knot.org
Describes a theorem for finding an area of simple lattice polygons. Includes proof and Java applet simulation.
Sliceform Models by John Sharp
mathsyear2000.co.uk
Three-dimensional objects constructed by slotting together a series of planar cross sections made from card. Downloadable templates in PDF, PS and Word formats.
The Geometry Junkyard
ics.uci.edu
Comprehensive list of links to sites on geometric properties of the shapes.