The proposed dock is not very pretty, but it is extremely cost effective (i.e. ~$2) and very easy to make. I'm sure fellow Instructables members will propose some great modifications.
1) A cheap iPhone dock. I got mine from a "very popular" auction site for $2 (this is a normal price).
2) general purpose white glue (optional)
3) a few zip ties
1) The dock has antislip material on the bottom. Flip the dock over, peel away some of the material to reveal two screws, unscrew them, and take everything apart. You will end up with three pieces - the top cradle, the PCB board, and the bottom piece.
2) What you do next is really up to you. Basically, you will want to secure the PCB board somehow. I simply zip-tied the board onto the bottom piece.
3) Plug the usb cable into the back and enjoy!
A few comments:
1) The only thing keeping your phone vertical while docked is the connector. This doesn't seem like a good idea, but I found that it was very, very firmly attached to the PCB board. For additional support, I applied some white glue around edges of the connector (the grey areas), avoiding any contact with metal or solder.
2) The "open" design of the dock might be an issue. The only solution I can think of is to cover the exposed sections with electrical tape. A more advanced solution would be to widen the cradle with a dremel and put the the top back on.
3) I really like this design because it works with most cases and is very "modular." I can simply disconnect the USB cable from the back and move it elsewhere.
4) It should work with any Apple device that uses the same connector and that can be charged via USB.