This morning on our way home from the dump an animal ran across the road in front of the car. My first thought was that it was the same color as the black squirrel that lives in our yard. My next was that it was a lot larger - longer, with a much thicker tail. I figured it was probably some kind of weasel. On looking it up when we got home, I found that it was what New Englanders call a 'fisher cat'. It's a North American marten - so, indeed, it is a member of the weasel family. Apparently fisher cats tend to be shy and secretive, more often heard than seen, as well as tending to be nocturnal so I consider myself lucky to have seen one.
(Image from http://www.catcustomer.com/fisher-cat/)