There is definately a knoppix for PPC. It just shows how poorly macs are represented
that few know about it.
Go here: http://debian.tu-bs.de/knoppix/powerPC/

I use macs infrequently, but think they are great. I had a G3 ibook but sold it-might get a G4.
Just mentioning that because I have done alot of searching on ways to use linux with PPC.

You might consider also Rock Linux http://www.rocklinux.org/

There is a thread at knoppix on PPC do a search.
here is one thread http://www.knoppix.net/forum/viewtop...=3646&start=60
Like all things for macs it's not as well supported

Good luck and if you find anything interesting share it!