Today, my Squeezebox (from http://www.slimdevices.com/) arrived in the mail. Its streaming server is written in Perl
I've only glanced at the code, but it looks very well layed out, and uses great modules like TT2 and DBIx::Class. And it's all GPL'ed too, nice!
If you're looking for a good quality, wireless media player, the Squeezebox should be on your list.