I have been looking into some of the options for streaming music from my WHS to devices in my house.
So far I don’t seem to be finding many good options. There are some that you point to a UNC share and then have to deal with a crappy UI to select the songs you want.
2 of the nicer options I have see are:
http://www.sonos.com/howitworks/
and
http://www.roku.com/products_soundbridge.php
http://www.roku.com/products_soundbridgeradio.php
I’m going to have to keep my eyes open for other options, but these seem like viable candidates.
Chris May 
You could also look into the SqueezeBox line of products (formerly SlimDevices, now Logitech) – http://www.slimdevices.com/
Yea, I was aware of Squeezebox before and I did look into it when I was doing this.
I’m trying to remember why I decided against it…. maybe I didn’t want to install their software on my server and was more interested in using the built in UPNP ability of the media server?
I’d be interested to see how the slim devices navigate a music collection.