I've re-enforced this design, http://www.thingiverse.com/thing:609693 and added a hole in the back to feed a usb cable and a rectangle hole to meet the bottom of the phone where you could fit the usb connector. I haven't actually tested this however, just printing now.
updated, works great, needs a way to weigh it down or secure it to a table.
Very simple. feed the charging cable in from the back. Put in hold in bottom where phone sites. Tack into place with a few small dabs of hot glue. Be careful as the hot glue can warp the pla if too much heat is applied for too long.
I could have made the hole more snug on the usb cable end as to not require the hot glue, but dimensions vary from cable to cable so the fair thing is to leave it generic. Also perhaps iphone cables can fit in there.