Ubuntu, Debian, Fedora, Arch...

I could have sworn I read somewhere that openSUSE was dropping PPC support.

Ubuntu is community-maintained now, but it's very formidable (I recommend the Alternate Installation ISO regardless of architecture...better experience post-installation). I haven't tried Arch on PPC yet, but I may. Debian has never failed me on PPC.

Issues to condsider? No Adobe Flash if you use that often on the web. Java is there, but not the official Sun JRE. There's a free software version called IcedTea that uses Sun's OpenJDK.