GSPlayer
GSPlayer is a an audio player for PocketPC. Features: MP3 playback using the MAD 0.15.0b; Ogg Vorbis playback; Wave format playback; HTTP streaming playback (MP3 / Ogg Vorbis); SHOUTcast streaming playback (MP3 / Ogg Vorbis); ID3 v1/v1.1 support.

MortPlayer
It's an MP3/Ogg player which is optimized for the needs on a Pocket PC. That's (among others) big screen buttons, simple playlist update from the contents of certain directories, and support of hardware buttons.

PocketMusic
Great freeware Pocket PC MP3 player with customizable interface, 10-band Equalizer, Visualizer, amazing Playlist Editor, Winamp playlists support.

WinamPAQ
WinamPAQ is a freeware MP3 player for your mobile device.
(PocketPC2000, Pocket PC 2002, PocketPC 2003, Handheld PC and CE.Net Device). It is fully compatible with most PDA's and is fully skinnable with most Winamp 2.0 skins.