I don't know. Copperhead? Look up Snakes on the web.
Yes, it's a copperhead. My neighbor (father of 3 small kids) was gracious enough to capture it so we don't have to worry about what we know. (of course, how many more are on our lot?)
He's going to release it tomorrow down in a nearby woods. I've seen a number of them in my outdoor travels, but this is the first on my own property. Note the distinctive triangular shaped head, and the coiled posture. Both key identifying marks.