It's been scientifically proven that cat purrs are healing! Just take a look at this article for example.
Here is an mp3 of my cat Roni, a.k.a Roni the Brat, purring away for your pleasure, relaxation, and healing. Enjoy! (Yes, that's his picture above!)
mp3 approximate length: 00:03:07.
mp3 approximate size: 2.27MB.