I've been trying to create a new partition on the 250GB drive I installed in my G4 (PowerPC) Mac Mini but I could not for the life of me find a Live CD that would boot. Finally this helpful post pointed me to Ubuntu 6.06 (Dapper Drake). After downloading the 'Mac (PowerPC) desktop CD' and burning it, I was pleasantly surprised to see it boot the Mac Mini beautifully (I used the live-powerpc kernel at the boot: prompt). Apparently the later PowerPC distributions of Ubuntu don't come with the necessary ATI drivers for the G4 Mac Mini!