The most interesting monsters of the 20th century by far were being animated on the screen by Ray Harryhausen. His amazing skills in the stop motion animation technique brought to life dozens of bizarre creatures. Something many people may not be aware of is the amazing conceptual artwork Ray has made to conceptualize the visions he brought to the screen.
This incredible fan site dedicated to the work of Harryhausen has compiled a great collection of the conceptual artwork made for each of his films. Click on the following film titles to see the conceptual artwork associated with each one.
The 7th Voyage Of Sinbad - The Golden Voyage Of Sinbad - Sinbad and the Eye Of The Tiger - Jason And The Argonauts - Clash Of The Titans - Mysterious Island - Earth Vs The Flying Saucer - First Men In The Moon - 20 Million Miles To Earth - The Valley Of The Gwangi - It Came From Beneath The Sea - The Beast From 20,000 Fathoms - One Million Years B.C.
There's also a great section dedicated to all the creatures in Harryhausen's films. Check it out here.
Click on the name of any creature in this list and a pop up window showing a short animated clip of that creature will appear, pretty cool.
You can purchase prints of Harryhausen's artwork at this site.
There is a small gallery of Harryhausen art over here.
And there is apparently a book that was published recently that focuses on the "sketches, key drawings, storyboards, and preliminary clay models" side of Harryhausen's work.