If you have a fast enough dual or quad-core CPU
And if for some reason you cannot play Nintendo games on the real thing as often as you would like to
or are simply curious about the games that Nintendo and its partners released after the N64 demise,
you might be interested in testing the updated version of the best Gamecube emulator to date : Dolphin v2.0
I use the 32-bit Windows version myself, but there are linux and (I know Ian will enjoy this) 64-bit Windows
versions available too.
Of course, I played a bit with the settings before creating this thread, and about half of the game images I downloaded work at full speed (predictably, with a few glitches), while a few would simply refuse to boot.
One of the dude who posts Dolphin videos on YouTube has its Dual Core overclocked @ 4GHz, so don't expect smooth gameplay if your CPU is not clocked above 3GHz (still, if you manage e.g. by using an older version to play those games you like smoothly with a somewhat less powerful config., good for you !)
Dolphin is supposed to be suited to play wii games, but I didn't try that yet since it's already rather challenging to get the most famous GC games to load / work (furthermore, I suppose the controls wouldn't fit an ordinary gamepad) at decent speed.
I have stumbled upon this update a few days ago, so obviously there are people more familiar than me with Dolphin out there. Also, those familiar with the N64 emulator Project64 might get the thing play GC roms faster than others due to a similar plugin architecture.
Needless to say, I own the GC games which I have downloaded "back up's" of, and certainly don't encourage anyone to get any GC rom if they are not in a similar situation.
Finally, there is a (too) small bunch of 2D games such as Legend of Zelda 4 Swords Adventure & Paper Mario that were released. Theoretically, Dolphin will play these without a hitch with default or close to default settings.