Just wanted to share the first Thing I uploaded to Thingiverse (which is a huge open-source collection of 3D-printable or otherwise fabricateable objects).
It's a 1/4-20 (standard camera mount) holder for a smartphone using a rubber band.
I saw many designs that use screws to hold the phone in place, but I didn't have such screws and I had many loose rubber bands. Also a rubber band allows the phone to snap in and out more easily.
It's a very basic 3D design I did with FreeCAD, then made it on my FlashForge Creator Pro.