There is Aragog the BIG spider in the forbidden forest along with the Centaurs and Hagrid's brother who is a giant. There is the Troll in the girls bathroom and the three headed dog that guards the Chamber of secrets. Just to name a few
Good ol' Buckbeak--the hippogriff! (also a mode of transportation...)
And yes, there was a bus...The Knight Bus, violently purple double-decker bus with tables and chairs in the day and beds at night. And thankfully for the passengers things magically move out of its way! Else Harry might never have made it to The Three Broomsticks!