All4Cellular offers the AT&T Apple iPhone 4 USB Car Charger, model no. 75367, for $4.95. Coupon code "POTW" drops it to $4.45. With $2 for shipping, that's $1 under our mention from December and and the lowest total price we could find. (For further comparison, we saw a refurb for $3 shipped last fall.) It features a USB port and is compatible with iPhone 4 / 4S. Coupon expires April 23.