I had a dream of a huge snake once, too, but I was awake. I'd just woke and saw a huge boa or python hovering at the foot of my bed, surrounded by a halo of long feathers and the impression of scaffolding around behind it. I looked at it, it looked at me. I wanted to touch it, but I knew it for what it was and that I'd ruin it if I moved, so I just sat and watched it. Eventually it faded away into the dimness of my bedroom.