That's exactly what I am looking for, too.
I use my notebook (Win XP) to manage and play music via Winamp. It would be so cool to output the sound on my Popcorn Hour via DLNA. I can do that via a Twonky app on my Android phone why not directly out of Winamp on my PC?
Is there a plugin or external piece of software? Any plans to add that as an official feature? Win7 can do it with Play-to and iTunes can do it with Airplay/Airtunes in combination with Airport devices. I used a software called Airfoil a lot to stream my notebook's sound to my Airports. But I wanna swtich to DLNA, as it is more open (e.g. support for Android devices etc.).
Thanks for any hint!