Summary

Most of today's smartphones are rectangles with rounded edges. Therefore I have designed a rectangle with rounded edge holder.

Instructions

The attached STL was generated for my HTC Evo 4G LTE. Open up the openscad file and attach the dimensions, round corner radius, and tolerance to match your phone and printer.

UPDATE: Better scad file and vertical iphone 4s stand

UPDATE2: Scad file now supports a tilt. Angles above 10 degrees not recommended, unless you make your base very wide. Uploaded tilt vertical stand for my EVO 4G LTE as example.

UPDATE3: Refactored and improved scad file. There should be no more strangeness with the bottom of angled stands. Also, steeper angles are supported, I've done up to 25 degrees with the phone on its side. Increase base thickness (variable bo index 1) to avoid having a hole where the phone rests.

Parametric Phone Stand