+Arnold K. at Goblin Punch blog has been doing some really interesting work on "mundane" animals in D&D.
I'm especially fond of his Really Good Dog class (some of whose powers resemble spandrels I've been thinking of posting here), and the gruesome-cute concept of catbooks.
I'm adding his blog to my "old-school blogs" roll to the left. Go show his site some love (preferably with face licks) on my behalf. If you're in need of adventure seeds for animal PCs, you can't go wrong tapping some of his wonderful ideas.