The Jacklamp™ is a new type of LED lamp package (Firewire™ and USB versions shown), designed to receive a plug and power from a bus cable, and provide light. (see Jacklamp™ FAQ)

Jacklamps utilize power from the billions of cables on hand in computer, instrument, industrial control, automotive, aviation, marine, and consumer electronics systems, to provide task lighting for setup, trouble shooting and repair in low or no light conditions.

A Jacklamp, in the absence of bus power (e.g. due to brownout, blackout, battery failure, or unavailability of a powered port, a powered hub, or an adapter-charger etc.) may be used on its battery powered accessory device (not shown), the Jacklamp Caddy™, as a portable handheld light, a cable extended handheld light or a cable tester/indicator. (see Jacklamp Caddy™ FAQ)

I have used a Jacklamp Caddy to power my USB light and iPod!