MuSE

MuSE is an application for the mixing, encoding, and network streaming of sound. MuSE can simultaniously mix up to 6 encoded audio bitstreams (from files or network) plus a souncard input signal. The resulting stream can be played locally on the sound card and/or encoded as an mp3 or ogg bitstream sent to a broadcast server. MuSE offers two intuitive interfaces (graphical and console) to be operated realtime and can also run in commandline mode.
http://muse.dyne.org

OLIVE

OLIVE is a stable, easy-to-use program-package for streaming (= broadcasting) live-audio in/to the internet using existing compress-algorithms like ogg or mp3. With other words, OLIVE is an internet-radio-sending-station especially designed for use by technically unexperienced people.
http://olive.ogg.at

xiph.org

Ogg Vorbis is a fully Open, non-proprietary, patent-and-royalty-free, general-purpose compressed audio format for mid to high quality (8kHz-48.0kHz, 16+ bit, polyphonic) audio and music at fixed and variable bitrates from 16 to 128 kbps/channel. This places Vorbis in the same competitive class as audio representations such as MPEG-4 (AAC), and similar to, but higher performance than MPEG-1/2 audio layer 3, MPEG-4 audio (TwinVQ), WMA and PAC.
http://xiph.org