openSCAD database of all convex polyhedra with regular faces except for prisms and anti-prisms. This includes the Platonic, Archimedean, and Johnson polyhedra (over 100 total!).
Pictured are all the Platonic solids and a few Archimedean solids created with the customizer.
I've also included platonic.stl for printing the 5 platonic solids, each scaled to be ~2 cm tall.
This was built on some previous work:
George Hart's VRML polyhedra models, (http://www.georgehart.com/virtual-polyhedra/vp.html)
In the customizer, there are 2 styles and 110 polyhedra to choose from. You can also adjust the thickness of the shell (default 30%).
In your software, orient the polyhedron so the largest face lays flat on the print bed.
platonic.stl has the 5 platonic solids (each created with the customizer) and will print in under 2 hours.
Some minor issues with the "cutout" style:
The cutouts for the faces are with respect to the origin, not the normal of the face, so some Johnson polyhedra which have faces with normals that do not intersect the origin will not have perfectly centered cutouts.
Face normals are not pre-computed, so rendering can be slow for large objects.