I have a (now discontinued) Griffin Technology TuneFlex Aux. This was a nice mount for iphones and ipods in that it came with a bunch of attachable adapters that would make your iphone, ipod, whanot, fit.
However, they had no such mount for an iphone4 (and indeed this device is no longer available from griffin.)
Instead of buying the latest and greatest they had I decided to just design and print an adapter that would fit and that would hold my iphone 4 nicel.
Not much to say here.. IF you have a TuneFlex Aux, you can just print this as it is and it should just fit and hold your iphone4 nicely.