It may be marginally morbid, but I love Skulls Unlimited, the "World’s Leading Supplier of Osteological Specimens." Sounds boring, but it really rocks.
For a start, they create custom skeletal mounts of animals that don’t exist (so say the scientists) such as this Centaur. The one featured here was created using the torso of a real human skeleton and melding it with the body of a horse.
Generally the company provides ‘run of the mill’ skeletons for research, however, as with the centaur, they also make some pretty awesome fake examples of hard-to-find, or non-existent, skeletons. The gallery features a penguin, beaver, marmoset, komodo dragon, rattle snake, lion and eland, barred owl, armadillo, dog (with toys) and monk seal.