KeyFinder - Key estimation software for DJs
VLC Media Player - VLC is a free and open source cross-platform multimedia player and framework.
Mixed in Key - Mixed In Key is award-winning DJ software that gives you the #1 technique of the world's best...
foobar2000 - An advanced freeware audio player for the Windows platform.
Tunebat - A browser based song key and bpm database. Supplies compatible songs for harmonic mixing.
Winamp - Winamp is a media player that allows users to play multiple-file formats, arrange media in a varied file-management system, and play unique media with AAC encoding.