This is a customizable Living Hinge, which I think was invented by http://www.thingiverse.com/SNIJLAB/about. The Customizer is designed to give people a feel for what my program can do. The idea for this is to simply add a living hinge in OpenSCAD with a function, and output a DXF that can be sent to a laser cutter.

The following parameters are customizable:
length = the y dimension of the hinge, parallel to the laser cuts
width = the x dimension of the hinge, transverse to laser cuts
d=the distance between parallel laser cuts
What is the minimum distance that two parallel lines can be apart before the laser does something catastrophic? E.g. setting uncontrollable fire to the work piece. This is "minimum_thinness"
hinge_length=the distance between 2 colinear laser cuts
hinges_across_length=the number of hinges across the length of the hinge
"center" is a boolean value, if true, place the center of the rectangle at the origin, if false, put the bottom left corner at the origin (just like square() and cube())

If you want to understand how they work:
http://www.deferredprocrastination.co.uk/blog/2011/laser-cut-lattice-living-hinges/

If you want to see the inventor's website:
https://www.snijlab.nl/en

Please leave any feature requests (OR BUGS!) in the comments. My hope is to add this as an OpenSCAD library.

See this thing's development in almost real time: http://forum.openscad.org/Living-Hinges-td18217.html#a18303

EDIT (26 AUG 2015): Added "add_hinge()" functionality, so now you can simply write add_hinge() circle(), to put a hinge in a circle. Thank you, Ronaldo Persiano.