Arcade Emulator based on SDL Mame. Many games for early arcade boards can be played with varying amounts of success.
Controls
Emulator Menu: WiiMote Home Button / GameCube L-Trigger
Insert Coin: WiiMote Minus Button / GameCube R-Trigger
Start (not all games use this): WiiMote Plus Button / GameCube Start Button
Up/Down/Left/Right - WiiMote D-Pad / Nunchuck Joystick / GameCube D-Pad
Button 1/2/3/4 - WiiMote 2/1/B/A / GameCube A/B/X/Y
Back (Exits current game) - WiiMote Plus + Minus Buttons / GameCube Z Button
Issues
Lots of ROMs are supported, but not all of them. If you don't see the ROM in the list in the emulator, then support for that ROM isn't included. This is to keep the size of the emulator low enough to run effectively on the Wii. A list of all the ones that are can be found here: http://www.toadking.com/wiimame.txt
Just because a ROM is supported does not mean it will run. Even games for early boards like CPS-1 can fail to run due to RAM limitations. If the emulator suddenly kicks you out to the Homebrew Channel, look in the MAME app folder (/apps/MAME) for a file called errors.txt. If it says something about failing to allocate space, then odds are the ROM can't run on the Wii. The emulator might also crash outright and leave you with a code dump if RAM runs out.
Only software rendering is supported. This makes playing games without using the frameskipper slow, but the auto-frameskipper feature is enabled by default.
No USB support yet.
Stereo audio is disabled.
The joystick on GameCube controllers can't be used.
The default UI font is way too small. A custom font is included, called Helvetica LT. (http://mrdo.mameworld.info/mame_artwork_supp.html)
Changelog
0.3 - October 29. 2009
Added support for many more ROMs
Fatal errors are now logged in errors.txt
More default control changes
0.2 - October 27, 2009
Fixed rom selection bug
Changes to the layout of the configuration files to make it more like other Wii homebrew