Is there a way to stream to my friends the song I am listening to in banshee or rhythmbox. I am not only asking for the ability to show what song I am listening to which works already by activating the Telepathy extension, but also to have a way to let them hear it while I play it. When I play a song they can also hear it on their PCs.
By this doing so we are able to broadcast the sound of our local sound card over the internet using a well established and stable protocol independent of local music players used (you could even broadcast the sound from a microphone).
This may not be a complete answer, but it's a start...
If you are using Banshee and your friend is also using Banshee, and you're both on computers that can use Telepathy, you can share your entire library with them using the
banshee-extension-telepathy available in the Software Center.
This is similar to DAAP for iTunes, except that it is not limited to your local network -- it can stream the music over the internet.
It's worth noting that this doesn't only share the song you are currently listening to (though it can show the current song in your chat status) -- it makes your whole library available.