A PowerBook 1400cs with a Sonnet Crescendo G3 upgrade card. I got it to work at some point, but then the HD died. My attempts to install Debian on a CF card and run it as a silent webserver have been mostly unsuccessfull sofar, but there is active development for a working kernel. It can be downloaded and tested from http://home.vrweb.de/internetzel/ and there is an active mailinglist at http://sourceforge.net/mailarchive/forum.php?forum_id=43985 which is part of the Linux/PPC for Nubus Power Macs project: http://nubus-pmac.sourceforge.net/
http://nubus-pmac.sourceforge.net/ Linux/PPC for NuBus Power Macs
http://www.icedtrip.net/guides/woody_1400.txt Detailed instructions for installing Debian Woody on a Powerbook 1400.
http://www.everymac.com/systems/apple/powerbook/stats/mac_powerbook1400cs_117.html