I just ordered this Bracketron Universal mount:
Grip-iT Vent Mount | Bracketron. I've had very good luck with their old iPod mounting kit (
iPod Docking Kit | Bracketron), but the SIII is going to be just a hair too wide for it.
Amazon had a deal on the Universal mount and a cup mount (
Amazon.com: Bracketron UCH-101-BL Universal Cup-iT II Mount with Grip-iT for GPS: GPS & Navigation), so I ordered both. I figure the cup mount could come in handy for rental cars.
I was intrigued enough by the Infuse mount to order it, too, but I have a feeling I'll be returning it. I like the idea of having an integrated power plug, but I don't care for window mounts. (I sit pretty low, so they block more of the windshield than I like.)