The best way to thaw something is to place it under lightly running water. Alton Brown had a great demonstration of that once. I tried it, and have been doing it that way ever since.
The principle involved is that of heat exchange. You don't need hot water - regular tap water is going to be warmer than something that's frozen. As the water runs over the item, it imparts heat to the item, thus becoming cooler. Since it is
running water, however, that means fresh water is immediately available to exchange
more heat into the item. It's amazing how quickly this works, even with a full chicken or a good-sized roast.
For the sake of reference, for those who may be able to find it somewhere, the Alton Brown show where he did that demonstration was the
Good Eats episode, "What's Up, Duck?"
HERE is a transcript, for those who are interested.