WiiMC (Wii Media Centre) is an open source media player for the Nintendo Wii. The GUI is powered by libwiigui.

Features:

Ability to play virtually any video or audio format
DVD playback, with DVD menu support
Picture viewer
Music player
Online media support, courtesy of Navi-X
SD, USB 2.0, SMB, HTTP, and FTP support
Attractive libwiigui-based interface, designed with the Wii in mind

Changes:

IOS 202 support removed
USB 2.0 support via IOS 58 added – requires that IOS58 be pre-installed
WiiMC channel updated – requires IOS58 and does NOT require a cIOS to install. Thanks to megazig and svpe for help with this
DVD support via AHBPROT – requires latest HBC or latest WiiMC channel
Synced to MPlayer r31961
YouTube support (thanks to lukegb and ataraxis for some help)
Picture zoom, rotate, pan, auto-rotate via exif data (thanks ataraxis!)
Fixed seeking for local FLV files
Fixed black-screen video issue with videos having widths over 1024
Fixed playback of MKV files
New YUV->RGB conversion in TEV for videos up to 720p (thanks sepp256!)
Restrict video loading to 720p (1280×720)
Enable caching of DVD CSS keys. They are written to the ‘css’ folder (created automatically).
Fixed playback of files with mono sound
Fixed issue with HTTP over-buffering
Other minor improvements/corrections

http://www.wiimc.org/