Study "Assembly.skp" (a Sketchup 8, free version, file).
Obtain the following parts:
1) "6VDC 45 RPM Pinky Finger Sized Gear Motor 1" Long x 15/32" x 3/8"" from either amazon.com or directly from http://sciplus.com/p/MICROMOTOR_47952. Other sources are available, I've not tested them though.
2) Coaxial Power Jack - Radio Shack part number 274-1583.
3) 3 Vdc Power Supply - Radio Shack part number 273-315.
4) 22 gauge wire.
5) Stick on felt pads.
1) This is a gear train design driven by a small dc motor at low current (1ma to 3ma, suitable for solar panel operation) which will require careful assembly with sanding, filing, and trimming equipment and skills for smooth operation. Take your time and test fit all parts and operation before final assembly.
2) Depending on the colors you print this thing in, you may require more or less sanding, filing and/or trimming. I've experienced varying results with different colors.
3) Lightly lubricate the gears with light machine oil (or very lightly with petroleum jelly or equivalent).
4) Break in the gear train by running the assembly at 6 vdc. After break in, the thing should work at 1.5 to 3vdc.
5) When the mechanism is assembled and broken in, slide "Cover.stl" over the assembly and attach to "Base.stl" using stick on felt pads.
6) The hats, printed in black, were glued to the top of the snowmen using cyanoacrylate. The eyes, nose, mouth and buttons were drawn using a fine tip permanent marker.
If you have any questions, comment and I'll do my best to answer them.