Linux/OS X Dual boot

Without reformatting your drive and making it two partitions, the best bet you have is buy an external firewire drive. Instal Linux via the external and you can use the OS X utility to choose your boot mode.
I have Linux on an external Firewire, but i rarely use it. Its more for fun or testing simple apps that I do not need OS X GUI for.

 

you can do it. note - not all linux distros have a ppc version.
my personal favorites for ppc are gentoo and crux. they might be a little challenging for someone new to linux though.
debian and mandrake both have ppc versions though

good luck. just follow the directions and it'll be simple.

it might just be easier to get a $200 throwaway PC and use that instead.

 

Yellow Dog Linux is worth a try too.

Much like a Red Hat Linux on your Mac, really. OpenOffice os pre-installed, choice of two GUI's and fun (with a nice boot-loader too )