The Gadget: The Griffin Charge Converter, which converts older Firewire-charging iPod docks and adapters to the newer USB charging iPhones and iPods.
The Price: $US30
The Verdict: For the most part, it works. The cigarette 12V adaptor in my car does not charge my iPhone 3G correctly, but if I plug in through this converter, everything's great.
The problem comes from the fact that it's a pass-through, so if you're not careful, the adaptor (and the charger) might snap off if bent too far in one direction. It also is awkward if you're plugging your iPhone into this, and then into a dock from the top without proper support. There's also the matter of it obstructing certain types of iPod/iPhone holders since they weren't designed to have something in-between the connectors.
But as for being able to convert Firewire charging devices to USB charging devices, yeah, it works with most devices, but there were two "older" docks that we checked that it didn't work with. So YMMV, since there are so many different iPod docks and chargers that have been made in the last five years. [Griffin]
Great when it works
Blocks or otherwise awkwardly arranges docking in certain chargers and accessories
Doesn't work with all older docks and chargers, which makes this moot if you've got one of the devices it doesn't work with