I use the car holder from Proclip. A little pricey, but it is custom-molded to my truck AND my device. When I change devices, all I have to do is change the device-side part, as the truck mounts stays put. I have 3 of these currently in my truck, with a fourth(xm) on the way.
URL is http://www.proclipusa.com/Default.asp
Of course, the martinjim/glacked franken-cradle and little double-stick tape would be cheaper and work just as effectively (I made my own for my desk)