Forum Moderators: travelin cat
If you don't have a copy of server, you'd probably be best served by downloading something like Audion from panic software or do a search for "mp3 streaming" at your favorite mac download site. (I like versiontracker, even though about 40% of the page is huge animated banner ads.)
There's plenty of options out there. Not exactly what you asked, but don't forget that iTunes can stream over your LAN automatically to other copies of iTunes.