The Feejee Mermaid and other Strange Curiosities
This place has a great collection of really weird monster sculptures and some vintage drawings of sea beasts.

Link found thanks to Pink Tentacle.

American Monsters
Here's a great collection of artwork of monsters that exist in legend around America.

Andrej & Olga Dugin
"The enchanting work of the husband and wife team Andre and Olga Dugin fills the pages of their unique re-telling of the Grimm Brother's story THE BRAVE LITTLE TAILOR. The duo (both originally from Moscow, now living in Germany) works in the tradition of Hieronymous Bosch or Peter Bruegel. In their version, which took over two years to produce, each corner of every illustration is filled with outrageous details; a gigantic fish sits in a birdcage, a tiny elephant walks upside down on the ceiling, winged salt shakers carry threaded needles."

2nd Gallery

Jüri Arrak
Much of Arrak's work is filled with blob like monsters.
There are many unusual beasts to be found in Arrak's paintings and drawings. Check out this dragon like creature.

2nd Gallery
3rd Gallery
4th Gallery
5th Gallery
6th Gallery
7th Gallery
8th Gallery
Single Image
Single Image