I received the Droid car mount as a Christmas present. I have the Body Glove case on my Droid and the Droid does not fit in the car mount with the Body Glove on.
Last week I purchased a Bracketron Mobile Grip-iT Device Holder With Rotating Vent Mount. It was on sale for $14.95 at Radio Shack. Now I do not like vent mounts, but I knew the holder used a single tab mount, where the Droid holder is a double tab.
I performed surgery on the Droid mount and removed one of the tabs. I used a Dremel tool to cut off the tab and smooth it down. The Bracketron holder fit on the single tab. I put the vent mount away in storage.
Next I played with some magenets until I found one strong enough to signal the switch ion the Droid for the car application and the location of the switch on the Droid. I attached the magnet with double-sided tape to the Bracketron Holder.
I have used this combination for a week in my Honda Element and it works perfectly. It swivels, using the swivel of the Droid mount, 360 degrees allowing me to position it any way I want - horizontal, vertical, etc. The USB charging cable attaches fine and it is not blocked.
It is a bulkier than the Droid mount, but I can leave the Body Glove case on the Droid and still have all functionality of the car mount.