Laser Cut Mendel Pulleys
This is a set of laser cut-able Mendel pulleys derived from a parametric OpenSCAD model I designed for this purpose. I plan to eventually make a complete set of configurations for the Mendel pulleys but in the mean time you can download the ready to cut drive pulley dxfs and it should not be to hard with the trusty OpenSCAD wikibook in hand to make the z driven pulleys (and then post them back here!).
Mendel uses belt pulleys in driving it's x,y and z axis as well as in it's driven z axis threaded rods. The problem is that many cheap 3d printers such as the Makerbot, RepRap, etc. are still working on being able to print accurate parts. The lack of symmetry in these parts caused by printer inaccuracy can then cause further inaccuracy in the child printer. This is a version of each gear in Mendel that can be cut by a high precision laser Cutter or CNC Mill so as to increase the precision of Mendel.
Reprap Stepper Shaft Gear
Another gear designed for thin plastic wafers - see thingiverse 
- not yet made. If you make these please add them!