Well, I'm kinda stumped. I'm following Brian's lead in playing around with the Ubuntu Linux "live demo" cd - the one that lets you test drive linux on a mac without actually installing it. Worked ok on my Powerbook (albeit rather slowly), but I can't seem to get my old 8600/300 to boot from the disk for the life of me. Searching Ubuntu Linux' documents turns up dead links. Google turns up references to BootX and yaboot (BootX for Old World Macs like mine, yaboot for New World Macs). I'll give up for now, but would love to get linux running on the old faithful Mac at home.
It's kind of funny, but all I need linux for is as a vector to get a current build of Firefox at home. I'm running a creaky old Mozilla build 1.3.1 so it's a touch out of date. And, my first reaction to the circa-1985 DOS bootloader on the demo cd was that MacOSX doesn't have anything to fear in the area of polish and usability. Still, it's worth some grief to get a modern browser at home, since I won't be springing for a new machine for some time (no matter how cool the new stuff is at MacWorld in January. Damn you, Apple ;-) )
Update: Found a page on the Ubuntu wiki that describes how to get it running on OldWorld macs - even how to convince it to boot from the Live Demo CD. I'll be trying that out soon...
Update 2: Gave it a shot last night, and although I did get the 8600 to boot from Ubuntu, I had to remove 2 PCI cards first. My old Quickdraw 3D accelerator and my just-as-old ATI Rage Pro VR cards had to be yanked to get Ubuntu to boot past a kernel panic. Then, I let the Live Demo CD chew for about half an hour, and eventually wound up with another kernel panic as it was 69% of loading up. Oh, well... It's running MacOS9 now, and it runs well enough that I can't justify taking the time to debug linux on it.