Docks are hard to come by for Android hardware, where very few individual models rise above the pack. But if you're one of 30,000,000 people sporting a Galaxy S III, or one of the considerably smaller number using AT&T's Samsung Infuse 4G, you can pick up an official vehicle mount for a song. Assuming that you can sing a song that's worth five American dollars.
The Infuse 4G dock is currently $29.99 on Amazon, but some wary forum poster over at SlickDeals spotted the same dock at AT&T's online store for just five bucks even. This particular model has been a favorite on XDA for a while, where user "ookba" (who had upgraded from an Infuse 4G to a Galaxy S III) noted that the larger phone fit in the dock just fine, thanks to the gently rounded corners. Throwing it into the cart on AT&T's store shows that the discount should apply for just about everyone.
Thanks to Samsung's uniform design for the GSIII, the dock should work for any carrier variant. And don't worry, you don't have to be an AT&T subscriber to make the purchase. If you want to pick this one up, don't wait around - at that price, it's likely a closeout, and it will go fast.