Reader Eric H sent me these screenshots I thought I'd share. They're of Debian/MintPPC Wheezy on an iBook G3 600 MHz with custom theming. Very cool.
Also, MacRumors poster Wildy left an update on a Crunchbang-like port for PowerPC, hopefully to be released later this summer. Screenshot is here.
So put one of these distros on your 'book, take it to a coffeeshop, and get ooos and ahhhs.