To my untrained eye it looks more like a juvenile African Lion (female?). Head doesn't look quite right, but the build of the body does.
Edit: After looking at photos, it does look like a cougar more.
[edit on 29-6-2007 by pavil]

Lewiston, Maine’s Sun Journal’s morning edition for Friday, June 29th, will be breaking the story of a new sighting and photograph of the following Mystery Cat.
John Goodine of Fairfield, ME
Jun 29, 2007 11:19 PM
Our lab at Elm City Photo processed this image straight off from his digital camera chip with no enhancements other than to lighten it. This was the best shot in a series of 4 or 5. Manipulated photos are generally brought in to us on CD roms or on USB Mass storage devices and not on camera chips as was this image. Hopefully we will be seeing more of these beautiful animals in our forests someday. Keep your cameras ready.
Originally posted by groingrinder
It is definitely NOT a Bobcat, or a Maine Coon Cat. Anyone who has actually seen either one of these knows that instantly. It is far too large for either one and it is the wrong color as well. It looks like a cross between a native Cougar and an escaped lion.
Maine Coon Cat
Bobcat