True, it may be a rat snake, but... do rat snakes rattle the end of their tails like a rattler would? That's what really threw me (after I thought about it). I mean... do ALL snakes do that when aggrivated? O.o?

if you have the pic in photobucket or Picasa, they give you the code to use (pick the HTML code). http://edis.ifas.ufl.edu/uw251 identifies all the common "black snakes" in Florida. Several of them have light chins, and none of those are poisonous.

It's a baby Black Rat Snake(Pantherophis obsoletta). Babies of this species hatch out boldly patterned with black blotches on a silvery background, and turn darker with each shed of skin, so they look quite different from the adults.

Unfortunately from this photo it is hard to tell. It is a dark colubrid and not a venomous snake. If I was to make an educated guess, I would say Jackson's Treesnake (Thrasops jacksonii).