Researchers have discovered that mice produce songs, presumably for attracting mates. After making audio recordings of the mouse sounds, scientists modified them to be audible to the human ear (they are normally too high-pitched to be detectable). To their surprise, the sounds were not just a collection of random noises--there was a pattern to them, much like birdsong. The really cool scientific implication of this finding is that mice--well-established as a genetic model for studying development and disease--might now be able to be put to use for studies of autism and other communication disorders. Birds are known to learn their songs, so researchers are very interested in finding out whether mouse songs are also learned, because very little is understood about how learning occurs in the brain, particularly when it comes to speech (communication). Previously, the only mammals known to learn new sounds were whales and porpoises, but these animals don't really make the best research subjects when it comes to studying molecular genetics.
You can listen to a recording of mouse song and read more here.