Dolphin is a Nintendo GameCube and Wii emulator for the Mac. It is a very nice emulator that has accomplished to let users play GC and Wii games on modern computers. Most games are said to work perfectly or with just a few bugs here and there. To play a game, you need to have the ISO image of the game CD. When you load an ISO, a new window will pop-up and the game will be played there.
The main window consists of a space where your ISO files will be listed. For each game, you will see its name, some notes, the size and state of the game and an icon that displays whether the game is for Wii or GameCube. If you move your mouse over the state of the game, you will be able to see if there are any problems reported with that game.
Dolphin has a great support for gamepads. You can use and configure up to four. You can even connect a Wiimote to your Mac and use that for Wii games.
There are lots and lots of emulation settings that you can change, but those are very technical and you might be better off not playing with them.
In my testing, I attempted to play two different games, both of which showed no problems in the state rating. Both started just fine, but after a few seconds, I got a white screen and nothing happened from there on. I tried Googling for a solution, but I couldn't find anything.