Summary

This clamp has no special purpose. It's the first part of a reading lamp that I'm designing.

My design goals are:

no vitamins (i.e. completely printable except electrics/electronics)
easy printing (avoiding excessive overhangs, etc.)
easy assembly

Update: added the sketchup file

Update 2013-04-30: Added stronger spring.

Update 2013-05-15: Added teeth in http://www.thingiverse.com/thing:89457

Instructions

Print each one of the left and right part with full infill. The spring should be one extrusion width wide, so each layer is printed in one continuous line for the most part. Slic3r tends to cut it into parts somehow, but I had no problems with the result either.
Maybe you will have to make the spring in a separate print, because it tends to come of the bed when the nozzle moves over to another part.

I printed with a 0.5mm nozzle and an extrusion width of 0.55mm. If you have any problems using other settings, please tell me.

When you're done printing, clean up the joint very thoroughly. Any bumps will avoid the clamp to open and close smoothly. After that, assemble the left and right part of the clamp by pushing the "male" part of the joint into the "female" part. You will need a slight amount of force for this. Then insert the spring as seen on the images and you're done.

Additional information for Ultimaker/Cura users:

It seems as if Cura has some problems with producing the gcode for the spring. v1.1 seems to produce better results, but still not as good as the same sliced wit slic3r 0.98. Please consider using another slicer for the spring if it shouldn't come out springy enough.

Kcs clamp