Sue Hendrix's Popup Workshop
http://l3d.cs.colorado.edu/~ctg/projects/popups/index.html

Popup workshop is a program to help you design simple pop-up cards, and print a pattern on your printer to cut and fold. This program consists of two windows, editor and viewer. In Editor window, you click on the folding line and resize the shape by dragging it. The program supports the only three shapes: rectangle, triangle, and trapezoid. However, it allows you to transform your shapes. The viewer shows you 3D look of your pop-up card. It also allows you to open and close your pop-up card using the slider, which let you control the range of angles. This 3D simulation function is helpful to you. The other helpful capability is to distinguish inward folding lines from outward folding lines by colors and line types. However, this program has a limitation: Designs of Pop-up cards are limited to several combinations of three geometries, because this program supports only three shapes (rectangle, triangle, and trapezoid). This program does not support diverse explorations to design your pop-up cards.