I just released MPlayerWii which is a native port of the MPlayer media player for the wii.
MPlayerWii - MPlayer for the Nintendo Wii
Containers: AVI, WMV, MKV, MP3, FLV (Flash Video), MP4, M4V, QuickTime
Video codecs: Xvid, DivX, Windows Media, MPEG 1/2, H264
Audio codecs: MPEG 1/2/3, Windows Media, AAC
-fixed screen color depth/banding issues (uses code from dhewg's mplayer port)
-added progress bar osd display during seek/volume on videos
-huge speedup on USB devices (thanks to rodries and Hermes)
-added classic controller support to position and scale the video display
-added file folders support
-added fix for PAL widescreen users (set the correct setting in mplayerwii.conf)
-much faster USB reading speed (huge thanks to rodries)
-mount/unmount the SD card and/or USB drive so you can swap them out without reloading MPlayerWii (thanks to rodries)
-added USB read-ahead cache (thanks to rodries)
-added preliminary samba network share support (thanks to scip)
-fixed startup crash when a usblan or usb keyboard is attached
-added network streaming cache
-added video scaling with the nunchuk (use joystick to move, Z button to stretch and C to reset)
-added configuration file (put in the SD root folder)
-new ascii logo by sensah
-happy french bastille day!
-added USB storage support (USB reading is dead slow unfortunately, only good for MP3 files)
-added volume controls (Up/Down buttons on the wiimote)
-added wiimote buttons repeat during playback
-added preliminary test network streaming (shoutcast and mms)
-longer filename display in the file selection screen
-fix for widescreen aspect ratio (uses the Wii display settings)
-more audio playback fixes
-added svenp's libfat patches (better read speed on SD cards)
-added pause button (A button on the wiimote)
-disabled MPlayer's error/status text during video playback
-file list now displays 20 files instead of 10
-improved audio playback code
- unzip the package into the "apps" folder on your SD card.
- place video and audio files on the root folder of your SD card.
- launch MPlayerWii through the Homebrew Channel.