The Cornell Lab of Ornithology just released an online archive filled with thousands of animal noises. The archive doesn't have _everything_--it mostly focuses on birds--but you could still waste a whole afternoon or more sifting through the aural wonders of Earth's many species. To wit: Did you know that a singing walrus sounds like a Tommy gun followed by a tiny spaceship floating away?
And did you know katydids make noises? Song-like noises, even.
You can also search by taxonomy, meaning you can peruse, at your leisure, the subtle differences between the Chilean flamingo: