Oz is a magical place full of strange and bizarre creatures of all kinds, many of which can talk, walk on two legs, etc... but not all of these can be considered "people" in the classic sense.
This is certainly not a comprehensive list by any means, so expect the unexpected!
Not all animals in Oz are Changelings. Birds sing in the trees, fish swim in the rivers, and animals scurry through the forests and fields. In addition to the native animals of Oz, animals have also been known to cross over with Storm Riders - some famous examples are Billina the chicken and Toto the dog, who came over with Dorothy.
Because of the fairy magic that imbues the land of Oz, animals have the ability to talk. Even Storm Rider animals gain this ability after coming over, though not all of them choose to exercise their new voices.
Also called "winged monkeys". They are controlled by whoever wears The Enchanted Golden Cap. Most are soldiers, scouts, or spies for Azkadellia.
The purple dragons of the north. They live underground and are allowed to come out once every 100 years for food.
Spiders famous for spinning webs that trap unsuspecting travelers and hypnotize them into becoming thralls.
A race of centaurs.
A group of trees that talk which reside on the banks of the Munchkin River that borders Munchkinland and Gillikin. They are usually quite moody.
Large, gentle creatures used for transportation across Lake Orizon. Eaten to extinction by the FearFish, a lake monster placed in the waters by Mombi. The Wizard of Oz used the bones of a Hippocampus to cast a ritual, bringing them back to life and turning the FearFish into a statue.
Horses with horns on their foreheads. They are served by blue dwarves and have a grove of silver apples, which can prevent hunger for seven days.
Giant red spiders who terrorize the forests.
A grotesque group of monsters. You don't want to know.
These horses constantly change color, gradually fading from one color to the next over time. You can often find these rainbow mounts used to pull carts and chariots, especially within the confines of the Emerald City, as they are considered especially fashionable.