i saw an episode of family guy where peter is a pirate, and his pirate friend is throwing "cargo" from one car to another. i don't think this is possible due to wind resistance. it would be cool to see if this was really possible.

Though depending on the size and weight of the object wind resistance may be a factor, that doesn't mean it isn't possible. You can always just throw it at a bit of an angle to compensate, or have the 'receiving' car lag a little behind the other car.

Back when I was young, stupid, and had no fear of violating laws, a friend of mine climbed out of my car and into another while driving 70MPH on the interstate(just so he could have a smoke) then did it again when he was done to get back into my car. I am certain that throwing objects is possible; but like Markov said, wind resistance can potentially have it's way.

it would depend on how much weight and mass the oblect has and how fast your going...besides its easy throwing apples out the window on the high way hahahaha

Yes, possible. It depends upon the wind resistance and you can compensate for it.
A few times I have thrown a bag of onion rolls through the open window of the van next to me, while travelling at about 50 MPH (I had forgotten to give them to the second driver, and we were both late). It was the middle of the night and there was nobody around. I would not recommend this activity, it is dangerous to take your concentration off of driving. Once, I/he missed and he had to stop and pick up the bag.

since the object you are throwing is going at the same speed of the car you are throwing it from, it might slow down a little when you let it go because it is not accelerating itself so it might not go where you want it to.

it takes a lot of tries to accomplish it, but successfully "air mail"ing a marshmallow from one car to another (unsuspecting) is well worth it.