Binary package hint: qemu
Althought the qemu package (version 0.8.0-3ubuntu1_powerpc) includes the qemu-system-ppc command for emulating PowerPC machines, it doesn't work because of a few missing files.
First of all, it's missing a ROM image. The file /usr/share/qemu/ppc_rom.bin is a symlink to ../openhackware/ppc_rom.bin, but this file does not exist. It can be gotten from the openhackware package from Debian, but this package does not seem to be in Ubuntu, nor is it a dependency of the qemu package.
Secondly, when the ROM image is installed, qemu-system-ppc complains about a missing VGA BIOS, which it looks for in /usr/share/qemu/video.x. However, that file does not exist. On other distros, it's apparently part of the qemu package.