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:
And its American counterpart:
Or, enjoy the otherworldly squeak of the Montezuma Oropendola:
There are a total of 150,000 audio recordings here, covering about 9,000 species. That's more than 7,500 hours of squawks, squeaks, and roars there for your enjoyment.