From Make Blog:
The basic idea is really simple: let’s put an iPhone (or Android) dock inside the little drawer-like ashtray. Let’s get it hooked up to the car’s 12V for recharging, and patch it into the stereo. For many old cars, this solves the very big question of Where The Hell Did People in the 60s and 70s Put Their Nonexistent Cellphones? Cars now are full of little nooks and power jacks and phone connections. Old cars, not so much. My old Bug didn’t really even have a good dash-nook to put a phone, or even a cigarette lighter for power. I installed the 12V socket years ago, and this ashtray conversion will take care of the rest.