I’ve been playing around with uPNP and TVersity. It is a central server that will allow you to easily access your digital media from other devices on your network.

It is PSP compatible.
It is free
It also works with XBMC
It streams music to a Nokia 770

It’s compatible with LOTS of other devices. Definitely give it a try:
http://s3.amazonaws.com/www.tversity.com/screenshots.html