A new Knoppix Live CD for PowerPC called Niktarix has been announced here:
Niktarix announcement
An early version is available as an ISO for download here:
Niktarix ISO
Niktarix has been built using kernel 2.6.11, binaries mostly from Debian Sarge, and KDE 3.3.2 as a desktop.
At the moment, the author has tested his work just on Genesi/PowerPC, i.o.w., not yet on a Macintosh or any other PPC platform.
Regards,
Walter.