This evolution of my Cube Gears incorporates my new snap pin design, which is much easier to insert, snaps more robustly, and prints more reliably. Included are plates for three different gear ratios (the ratios are the numbers in the filenames).
If you need the parts individually, you can export them with Customizer. You can also add custom embossed text to the large gears.
UPDATE: Minor update from pin library. See Instructions for details.
I would recommend snapping the pins into the center block first, then putting the gears on. Sometimes the inside of the hole in the gears is not very strong (if you print with low infill) and the pin can break through if inserted into the gear first.
UPDATE: You shouldn't have to worry about weak pinholes anymore. I updated the pin library and this design to incorporate small slits that fool slicers into creating internal webs for added strength.
You should also apply some grease to the pins (I use white lithium grease, but anything should work), which makes them easier to insert and remove and makes it turn smoothly without squeaking.
Only the pins are interchangeable between the different ratio cubes; they all have different center blocks. The larger gears go on the larger faces of the center blocks. I print these on the MakerWare medium default settings in PLA. Support is not necessary.