Vorbis is an open source patent-free audio encoding and streaming technology that is part of the Ogg container and created by Xiph.Org. Vorbis was made to replace other propriety audio encoding formats like MP3, WMA, RA, AAC, and VQF. Vorbis not only compresses better than those format, but it also sounds better as well. Vorbis is a lossy codec.

Vorbis gets its name from the character Vorbis in the Terry Pratchett book Small Gods.

Program plugins to enable Ogg Vorbis support.

WinampPlugin-OggVorbis129.zip - A Winamp plugin to support Ogg Vorbis playing. (121KB)
NeroPlugin-OggVorbis.zip - A Nero plugin to support Ogg Vorbis burning. (204KB)

vorbis.com - Vorbis' official site.
Why Vorbis - An essay on why you should use Vorbis.