Nice shots. Do you have DOF preview on your camera? I think the second photo would have a lot more impact if the snake was completely within the focus field.
"DOF preview" ... is there anything like that in the 350D (Rebel XT) ???
I always just guess...
And you worked your DOF nicely though in the first I personally would have preferred to see more of the foreground boots in focus and not so many of them out of focus before we get to see them sharp. Your camera produces a pleasing bokeh, you could have played with that more, I think.
And I agree on the snake-shot: particularly the fact that its HEAD is no longer in focus is a bit of a pity here.