I have a few DC adapters around here that I have had for a while that plug into the DC outlet in my car to power my USB gear like the iPhone and more. The catch is that the chargers I have for the car lack the amps needed to be able to charge my iPad. If you plug the iPad in it gets no power. If you travel with your iPad a lot that is not a good thing.
A new DC charger has surfaced from iKit called the AutoCharge + USB and the thing will charge the iPad and any other USB charging device. The iKit offering provides 2.1 amps via a single USB port. The low profile device should fit in DC outlets in your car that are small or crowded too. It comes in white or black colors.
The charger also ships with a coiled USB cable that has an Apple charge adapter on one end. That means you can leave you normal cable at home and use the cable that comes with the AutoCharge + USB in the car. The device is available now for $24.95.