All4Cellular offers the AT&T Apple iPhone 4 USB Car Charger, model no. 75367, for $7.95. Coupon code "NEWSLETTER" bags free shipping. That's the lowest total price we could find by a buck. (For further comparison, we saw a refurb for $3 shipped in October.) It features a USB port and is compatible with iPhone 4 / 4S. Coupon expires December 27.