Just a starting point...I've got a ton of ripped media on the home network that I'd like to be able to play on the PS3, but I've not been able to find the bits necessary to get it to work.

For right now, here's a few links that get a little closer on making it happen.

http://www.mythtv.org/wiki/UPnP
http://www.gnu.org/software/gmediaserver/
http://ushare.geexbox.org/
http://code.google.com/p/ps3mediaserver/

They all say "LINUX" which may require some tweaking because I'm serving the stuff off a Solaris machine, but we'll see. I'll try to keep everyone updated.