Really...do you still have a cassette deck in your car. I know I do. Ever notice how the cassette kinda sticks out but is held firmly when its ejected. It makes a perfect iPhone 4.0 stand. All it takes is a cassette you don't care about and a Dremel.
Step 1: Assemble Your Stuff
You'll need a clamp, a Dremel, a cassette, a pencil, your iPhone, and your car charger.
Step 2: Rewind the Cassette.
My car player is broke, so I used a pencil.
Step 3: Measure Out How Much to Cut.
Simply draw a line on the side of the cassette that doesn't have tape in it. I measured the width of the phone.
Step 4: Start Cutting the Top.
Clamp the cassette securely, and just go at it across the top. Dont go all the way, just cut out one side of the tape.
You should have a nice clean rectangular hole. Dont go so fast as to melt the plastic! Also Don't go so slow because it will crack the tape. Try a slow speed and if it kinda 'chatters' slowly increase the speed. I was going about 30%-40% speed on my Dremel. I'm using a Tungsten Carbide Cutter here, but you could use any sort of bit. Just make a hole in on the face of the cassette, straighten the Dremel and route out the area.
Step 5: Remove Bits Inside the Tape.
Any paper, film, or rollers, just pull them out. Make sure you drill out any housing, screws, rollers and such. It should be clean inside.
Step 6: Drill Out the Charger Hole.
Cut a line in the side of the tape for the cable to snake into the stand. Cut a smaller hole on the bottom for the adaptor.
Step 7: Done!
Make sure everything fits, including the cable. You should be able to easily attach the charger cable, and drop it in place. File away slowly to get a snug, not loose fit.
Put it in your car and enjoy!