Feature Request
An audio only option in the Chrome Cast extension like "Cast screen/window (experimental)". This would allow me to cast the audio output from applications like Winamp, iTunes or Windows Media Player. It would avoid the distraction of mirroring everything I do on the PC and could perhaps use the default backdrop as a video display.
I could set up a DLNA media server, except that the server's are universally rubbish and so are the clients. There's a separate feature request there that Chromecast acted like a DLNA renderer client. That would allow the use of the WMP "Play To" function.
A "Cast Audio" should be trivial seeing as they already have a "Cast screen/window" function which already grabs Windows audio output and redirects it. And that would avoid being forced to stay inside the Google ecosystem just to play a music track.
Let's say we (the public) wanted iTunes or Windows Media Player to become Chromecast aware. Who's going to do the work? Because it's not going to be Apple or Microsoft, right.
I kind of doubt an extension would be good enough for that level of directness.