It's a Green Tree Frog, also known as hyla cinerea. We think this guy (or gal?) was a youngin' because he was only about an inch long or so in the body and his feet were very bright. After they are full grown, they are just a tad bit bigger and their feet aren't quite as fluorescent.
We found a cool website to help us identify all kinds of frogs in Tennessee. You can even listen to the sounds they make through the .wav files. Here's the sound of the Green Tree Frog. Very cool!
Not too long ago, we were walking the pasture when this little 'thing' took a hop right in front of me. At first Mum thought I stepped on a piece of bark, but then we saw it hop away...it was a Southern Cricket Frog. Here's the photo example, courtesy of Walter W. Knapp, on the State of Tennessee frog site.
During the heat of summer we would hear a chorus of frogs singing throughout the night, along with the crickets and the Cicadas.