Wii MOD-CHIPs

Hardware you need :

An SD Card
An action replay kit for GC
The Action Replay for Gamecube costs ~$25 but as well as being the device needed to boot homebrew its also a Region Free Gamecube Boot Disc and Cheats Device, well worth the cost.
An SD card adaptor for GC: Home Made, Nintendo Made or the Gecko (the best )
SD Card Adapters are a bit harder to find t, Buy the Gecko version if you cant find the Nintendo Adapter. There's a 64MB USB Gamecube Memory Card at Play Asia that would take away the need for a SD Card / Adapter at the expense of less space. Its untested at time of writing but a fair bit cheaper than buying separate.
And of course Nintendo Wii console - USA, JAP or PAL Consoles are all compatible.

The Tutorial

1) Plug your SD card into your computer - format the SD card to either FAT or FAT16 (not FAT32 as it will not work). After formatting it run sdpatch.exe through the command line as follows:
sdpatch.exe (drive letter):/
now copy SDLOADER.BIN to the root of the card, at this point you can load it up with emulators and what not as long as they are in GameCube .dol format . They can be in any directory as long as SDLOADER.BIN is in the root.

2) After installing the above insert SD card into GameCube SD card adapter and plug into Wii Game Cube memory card slot A. Insert your action replay card into B and the disc into that place where discs go.

3) When Action Replay boots up pick the USA flag and then ADD NEW GAME. SDLOAD is the game name and push done. Then enter (m) as the code name. Enter the following code

7YPR-RKZZ-MH6W5
D26A-PE4J-1XX2W
ZJHY-B1ZH-6P00G

Then select ADD NEW CODE and name it SDLOAD. Enter the following code

Select the code named SDLOAd and check the box next to it, press start and Open and close the lid of disc drive when prompted. Then SDLOAD starts up and you can take it from there!
The Code Process is a one time thing and from then on you can enjoy the world of Gamecube Homebrew and Emulators on your Wii Console easily and without Modification.

Emulators for Gamecube that will work this way include emulators for Snes, Genesis, GameBoy Advance, Gameboy Color, PC Engine and Nes and also a port of Doom.

OR You can use a MOD-CHIP to play GC roms from DVD

WiiKey mod-chip GC Audio Streaming fix etc. Reagion FREE run different NTSC region Wii Game Backups on US and JAP Consoles. Enables direct boot of GameCube backups. Homebrew SNES NES MAME SEGA emulator rom support! Supports full size 4.7 GB DVDs for GameCube Homebrew so no 1.4 GB limit like on GC.

Wii D2CKey modchip