This fully working 12mm 3x3x3 Cube is nearly five times smaller than the original Rubik's Cube - it is far smaller than just a single cubelet of its big brother. It is printed in one piece, without the need for assembly. A thin layer of wax keeps the parts separated during printing, which is then melted away to yield this fully functional Rubik's Cube.

IMPORTANT - READ BEFORE BUYING
Since Shapeways' can not remove all of the wax themselves, you will probably have to do some work to get your print to turn. You should boil some water and put it in a cup along with your cube. Leave it in there for a few moments, and stir to help speed up the wax removal. Then remove from the cup with a teaspoon, and (being careful not to get burns from the water) gently move one or more sides. You may need to put the cube back in to the water to melt more wax and continue this process untill all of the pieces are freed up. You may also need to use a small knife to help separate some pieces. Note that if the wax cools down, the puzzle may become more difficult to move.
Since the heat also softens the puzzle plastic, it is very delicate when warm. You should take extreme caution while removing the excess wax. Neither Shapeways or me can take responsibility if your puzzle breaks during this process. It might therefore be recommendable to order more than one copy of this puzzle.
It might make things a lot easier if you put soap in the water, that might help dissolve the wax. I haven't tested it myself but it sounds promising.