TCPMP - The Core Pocket Media Player is an open-source media player for Windows Mobile-based devices.
Supported file containers: AVI (*.avi), Matroska (*.mkv, *.mka), MP4 (*.mp4, *.m4a), Ogg Media (*.ogg, *.ogm), ASF (*.asf).
Supported audio codecs: Mpeg 1 Layer III, Ogg Vorbis, Musepack, Windows Media Audio, AC-3, AMR, Adpcm, uLaw
Playlist Manager - Create and edit Windows Media Player playlists directly on your Smartphones!
Windows Media Player for Smartphones doesn't have a built-in feature of creating playlists. One option is to create a playlist by means of some available utilities using the PC
Kinoma Play is the world's first mobile media browser. It is everything you need to find and play video, audio and pictures, whether they are on your phone, on your home PC, or on your favorite web services.
Video
Share the YouTube clip that made you laugh out loud. Catch breaking news updates from Reuters. Watch recorded TV via your home PC, or bring it with you
Pocket DivX Player is an open-source multifunction video and audio player for the PocketPC platform that can play DivX, OpenDivX, Mpeg-4, Mpeg-1 videos and Mp3 audio
SmartAmp is an audio player of files in format MOD and XM. There are plenty of free MOD files on the Internet, so if you like them you can use this program to play them on the Smartphone.
Note from SFD:
SmartAmp was initially intended to play MP2/MP3/OGG/WAV/RAW/MID/MOD/XM/IT/S3M files. But this project was frozen back in 2003 in the Alpha stage
mPlayer is one of the most popular Linux/Unix media player. Now, thanks to XDA-Developers forum member amitv_17 its ported for Windows Mobile devices.
Everything is still under development but most of the usual features are already available plus support for the basic audio/video formats like AVI, WMA, MP3, OGG etc