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 (requires IOS 202)
Picture viewer
Music player
Online media support
SD, USB 2.0, SMB, HTTP, and FTP support
Attractive libwiigui-based interface, designed with the Wii in mind

Changes:

Fixed issue with browser reloading
Fixed freeze on seek issue
Fixed a back-to-menu freeze
Changed stereo downmixing
Added codepages
Translation updates (and added Hungarian and Polish translations)
Other minor changes

http://wiibrew.org/wiki/WiiMC