The end plates of a Sarrus linkage stay parallel and move along a straight line. This allows linear motion to be created without linear guides. Video is here: http://vimeo.com/72531195
This model can be printed (nearly) fully assembled and without any support material. Also, this model can be modified in Customizer to produce linkages of any length, as well as linkages with two or four sides.
Set the linkage parameters and print. Most the hinges are printed fully assembled; bend them a few times after printing to loosen them up.
You will need to snap the last hinge(s) into place. It's a little tight, but with some patience and steady pressure the last hinge will snap together.
The hinge spacing parameter controls the clearance between adjacent hinge fingers.
In my experience, if there is a gap between adjacent hinge fingers when printing the first few layers, then this parameter value is large enough. The default value, 1mm, worked well on my printer with a .4mm nozzle. If you start printing and the hinge fingers overlap in the first layer, cancel the print and increase the hinge spacing value.
The hinge length parameter can be used to increase the clearance around each linkage arm, allowing the linkage to retract more.