Subsonic
http://www.subsonic.org/pages/index.jsp
'Subsonic is a free, web-based media streamer, providing ubiquitous access to your music. Use it to share your music with friends, or to listen to your own music while at work. You can stream to multiple players simultaneously, for instance to one player in your kitchen and another in your living room.
Subsonic is designed to handle very large music collections (hundreds of gigabytes). Although optimized for MP3 streaming, it works for any audio or video format that can stream over HTTP, for instance AAC and OGG. By using transcoder plug-ins, Subsonic supports on-the-fly conversion and streaming of virtually any audio format, including WMA, FLAC, APE, Musepack, WavPack and Shorten.'
Basically, you install a program on your computer which makes it act as a server. Then you can stream your music to any other computer/phone/etc out there.
It's pretty awesome. You basically create an admin account for yourself, then you can create as many username/password combos as you want to give out to people so they can listen to your music.
I just setup a server today for all my music. And Ive given the address to a few people on irc to test.
I havent fully explored the capabilities of it, but so far it's a neat program since I can stream my music on my phone (no need for an ipod anymore) or at a friends house etc. And I can give friends access to the server so they can listen to my music also.
If anyone decides they want access to my stream, just bug me about it.