I purchased a GL yesterday. I was working through many of the questions associated with iPhone use. I don't recall seeing a post on this adapter so I thought someone might find it useful.
The Scosche Firewire to USB adapter converts the pin out on the factory iPod kit in the MB to charge the iPhone 3G. The adapter cost about $25 dollars at my local Apple store and seems to work well.
Here's a link:
Scosche Passport FireWire-to-USB iPod adapter gets reviewed - Engadget 
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