PicoStreamer audio/video live streaming server is a set of CGI (Perl) and PHP script to set up your own web radio. It works on a normal web hosting (Linux) and you don't need an expensive dedicated server.
Also, due to HTTP protocol used, you can stream data to server behind a NAT/Proxy/Firewall and you listeners can do the same. It's included PicoIcy, a client for streaming to PS server using your preferred Shoutcast/Icecast source encoder. PicoStreamer is an Open Source project.