I had a Wallstreet 292MHz (oldworld, but still with the neat wetsuite design like the Lombard

) and I was very happy with both
Debian-PowerPC and
YellowDog Linux on it. YellowDog is more RedHat-like while Debian is...well...Debian.
Mandrake also has a PowerPC port but I never used it, the same goes for Gentoo.
Håkan