foobar2000 is an advanced audio player for the Windows platform. Some of the basic features include ReplayGain support, low memory footprint and native support for several popular audio formats.

Features:

Open component architecture allowing third-party developers to extend functionality of the player

Audio formats supported "out-of-the-box": WAV, AIFF, VOC, AU, SND, Ogg Vorbis, MPC, MP2, MP3

Audio formats supported through official addons: MPEG-4 AAC, FLAC, OggFLAC, Monkey's Audio, WavPack, Speex, CDDA, TFMX, SPC, various MOD types; extraction on-the-fly from RAR, 7-ZIP & ZIP archives

Full Unicode support on Windows NT

ReplayGain support

Low memory footprint, efficient handling of really large playlists

Advanced file info processing capabilities (generic file info box and masstagger)

Highly customizable playlist display

Customizable keyboard shortcuts

Most of standard components are opensourced under BSD license (source included with the SDK)