As noted by the title, this is a set of dice that are rounded like spheres. In the download I have included 8 stl files of the different dice in the set, a d20, d12, d10, percentile d10, d8, d6, d4, and d3, the OpenSCAD file that I wrote to make them, and a java program that I wrote to find the positions for the numbers. The dice in the model are decently small at 2cm in diameter, but with the OpenSCAD file, you should be able to make it of any size and make dice with other numbers of faces than listed here.

(If you do choose to use the OpenSCAD file, to use the numbers you will need this: http://www.thingiverse.com/thing:16193)

In regards to printability, I will say that these are pretty difficult to print for at least my printer considering the extremely small base and multiple overhangs, though I'm sure someone out there is able to print it just fine.