Had the idea to use a mason jar as a shade/globe on the pendant lights hanging over the bar in my kitchen. Found that I had a large mouthed large mason jar that would fit over the bulb and thought it would work great and look good as well. I recalled the hummingbird feeder (http://www.thingiverse.com/thing:77439) I made last year, and thought I might be able to re-purpose the lid, so that is exactly what I did! I started by re-sizing the lid so that it would fit a large-mouth jar, and chopped off the center section so that it wasn't quite so thick. Then I used the Nut-Job customizer (http://www.thingiverse.com/thing:193647) to make a 'bolt' that I could use to carve out or subtract from the inside of the ring so that it would thread onto my fixture. It ended up being 42mm and a thread step of 3.5 seemed to match the threads on the ceramic piece in my light fixture. I printed two of them in brown ABS and they took about 40-45 minutes each on my FlashForge Creator Pro.
IMPORTANT, the bulbs you see pictured are actually LEDs and thus do not create much heat, I would NOT recommend using incandescent bulbs with these without checking to make sure they do not create enough heat to melt/burn the ABS or whatever material you use!!!