http://www.debian.org/ports/powerpc/
or
http://www.yellowdoglinux.com
Yellow dog is RedHat based. Most software should compile OK but not all.
Hope your mileage in downloading the ISO's for Yellow Dog is better than mine, took ages to get them down (eventually got them from Poland via
www.filemirrors.com) and that was with a T1 that I only share with 1 other person (and he wasn't using it after he wrote a little proggie to slurp down all the roms from mame.dk, too busy playing arcade games, all 5Gb of them ;>)
Don't forget to run
www.maconlinux.org , it freaks the tree-huggers out to see their beloved OS running on Linux.
Now if only I can convince them of the beauty of the GIMP...........
Flibble