Saw someone asking about evolution and creature design the other day somewhere on CA which got me thinking about my previous academic occupation, Biology =). So here's a big ol' list of wikipedia links of various topics dealing with critters.
A lot of the wiki articles will have multiple subtopics/links on them and usually some general examples associated with the classification for ease of use.
Anatomical Terms of Location
Anatomical Terms of Motion
Animal Locomotion (this has multiple subgroups including flight/swimming/terrestrial)
(all of these have multiple subgroups, interesting reads)
-Tetrapods - Vertebrate, 4 Legged/Apendages
Cartilage Fish (Sharks/Rays)
Insects, Crustaceans, Arachnids
Squid, Snails, Bivalves
Jellyfish, Coral, Sea Anemones, Hydras
Starfish, Sea Urchin