De-coder.com

GSpot Codec Information Appliance
Tool for identifying what codec a video file uses and what codec your system need to play it. Distributed as freeware for Microsoft Windows.
www.headbands.com/

The Ogg Vorbis CODEC project
Open source audio format.
www.xiph.org/

TTA free lossless audio codec
TTA lossless audio codec is a free, simple real-time lossless audio encoder/decoder.
www.true-audio.com/

Isdn Audio Codec
Offers ISDN audio codecs for sale direct to broadcasters and individuals. On-site discussion forums and advice sections.
www.isdnaudio.com/

MPXPLAY
DOS player that supports mp2, mp3, aac, ac3, dts, ape, mpc, ogg, wav, and cd.
www.geocities.com/

Winamp
The leading high fidelity music player for Windows 95/98/NT that plays MP3s, MP2s, WAVs, VOCs and MIDIs.
www.winamp.com/

Apple - iTunes
Free MP3/AAC player/organizer for Mac and Windows that tags, rips, burns and converts audio files and integrates with the iPod portable music player and iTunes music store.
www.apple.com/

Free Lossless Audio Coder
FLAC is an open source lossless audio codec, supports streaming, seeking and archival.
flac.sourceforge.net/

Steve Ekblad's Free Audio Software and Online Audio Tools
A variety of acoustics related software tools geared toward the do-it-yourself experimenter.
www.audiogrid.com/

XMMS
X Multimedia System, an open-source MP3 player for Linux. Contains mostly the same features as Winamp and supports skins.
www.xmms.org/