For all the lovers of old news out there, here's a post for you: the dog-toting running board sack. It was published in Popular Mechanics in 1936 and still remains the safest way to travel with your pet.
When you take your dog along for a ride, but prefer not having it inside the car, it can ride safely and comfortably in this sack, which is carried on the running board. The bottom of the sack is clamped to the running board and the top is fastened to the lower part of an open window with hooks, covered with small rubber tubing to prevent marring the car.
I know what you're thinking, and yes, this is a great idea. I'm going to build one for my wife's dog and take her for a spin around town. I'll let you know how it goes.
UPDATE: Okay the dog bit me and refused to get in the sack. Luckily I'm babysitting my little brother later so maybe he'll want to go for a ride.
UPDATE: I backed over him. It's okay though, I was smart enough to test the sack on a bike first before moving to a car. I've made a few modifications, and I think he's down for another go at it.
UPDATE: Okay, I think he's somewhere between the gas station and the movie theater.
Modern Mechanix Round-UP [boingboing]