Yugster offers the LifeBox UltraCharge 10,000mAh Portable Power Bank and Car Jump Starter, model no. UC10000, for $39.97. Coupon code "DNLIFEBOX" cuts it to $38.97. With $5 for shipping, that's the lowest total price we could find by a buck, although we saw it for $4 less in October. It features jumper cables, LED flashlight, USB adapter cable, iPhone 4 USB cable, and two USB ports.
Note that the countdown timer on the product page does not reflect an actual expiration time and resets daily.