We've been fortunate to be able to examine some 3D printed objects from Objet in their Vero Clear material first hand. While we've seen clear (and clear-ish) items printed before, there seems to be advantages when used in a multi-material 3D printer.
A multi-material 3D printer can build objects in more than one material at a time - and that is a feature on many devices in Objet's 3D printer line. We've now seen several objects made by combining clear material with non-clear, yielding some very interesting results. Consider this hand - complete with interior skeleton!
Objet has posted this image of simple clear cubes, each containing apparently (and actually) solid objects. The high resolution of their 3D printer permits these tiny objects to be embedded in the clear material.
We observed similar approaches at the Pompidou Centre in Paris where Objet displayed artwork from Neri Oxman. Clear mixed with black is an amazingly useful technique.
Finally, if you don't like mixed colors, consider this image lenses, again produced on an Objet device using their clear material. The item on the left is a lens as it emerges from the 3D printer. The item on the right is the same object after polishing. We can verify that it's sufficiently clear to see through.
Finally, 3D printing has reached a level able to produce cheap sunglasses!