Stream music to many computers on LAN
As simply as possible:
Install VLC onto the "server" of the music. vlc-nox is a handy package in the Linux world.
Run VLC on "server" as something like vlc *.mp3 --sout rtp:224.0.0.1 --ttl 4
224.0.0.1 means feeding the data out to the multicast All Hosts group.
TTL 4 means only cross at most 4 routers which should be more than adequate for any small LAN
On any workstation machine now connect to rtp://224.0.0.1
See http://en.wikipedia.org/wiki/Multicast_address for the different types of multicast addresses