This is a variation of the car iPhone dock that I have documented here:
It uses the same combo USB and Audio Line Out cable linked from that page. I've included an STL as well as the original Autodesk 123D file. If you are interested in learning Autodesk 123D the above link also includes a video tutorial on how I constructed this 3D model.
Printed in PLA on a RepRap Prusa Mendel. Legs were glued on with E-6000 adhesive