Cable Holder Hemisphere (Small Cables)
Inspired by http://www.thingiverse.com/thing:70549. I needed something with a smaller opening to keep my cable...s from falling out, so I whipped up something similar. It holds the USB cable for a Samsung Galaxy S4 perfectly. It takes just a small amount of pressure to "snap" it into the holder; enough to hold the cable, but not enough to damage it.
Just about any material would work well depending on what you're looking for. Flexible filaments, especially the harder TPU, are a great choice as it ...allows the lips to give a bit when inserting cables.