The Dragon from 7th Voyage of Sinbad was the first dragon I ever saw in a movie and is still my favorite of all time.
Vermithrax Pejorative from Dragonslayer was also an early favorite.
More recently, the Fell Beast, or the Witch King's Dragon from the Lord of the RIngs films, was pretty cool, I thought. Too bad he hegts his head cut off!
...and there's the classic Disney Dragon from Sleeping Beauty.
Can't wait to see Smaug in all of his glory!
I had a burger for lunch and I feel guilty:(
EDIT: I forgot to add the Eborsisk, a two-headed dragon from Willow. This guy's cool as well!
If you get to see Smaug, he's reaaalllly cool. Saw the movie this weekend. Lots of fun!