Doing some research and stumbled across a wonderful piece of video...
http://www.youtube.com/watch?v=UEgzXw9u9eE
The list of movies is given on the right. I can recognise several of the creatures on the first go, but not all of them.
See if you can name all the monsters. To start off, I ll list those which I know of -
Audrey II
Facehugger
Bruce
Kong
Stay Puft Marshmallow Man
Godzilla
Balrog
Anaconda
American Werewolf
Kraken from Clash of Titans
Grendel
Demon Dog from Ghostbusters
Predator
Baby Alien
Sandworm from Dune
Gremlin
Medusa
...