Monk has released a new Gamecube emulator for windows and linux, heres info from the read me file:

This is the first release of gcube - an open source gamecube emulator. I'm writing it only for educational purposes. My aim is to make at least one commercial game fully emulated (that means with sound and original speed). This release is aimed at homebrewn programs. There is no gui and no gcm support (so no comercial games are running).
Main target platform is Linux / x86. Windows is not fully supported at this point (emulator seems to work, debugger doesn't). I would also like to support Mac (at least with interpreter), but I don't have access to one, so it will have to wait.

Download here -->