I have a pre-firewire Blueberry iBook for sale. It features:
300 Mhz G3
6 GB HD
128 MB RAM
Mac OS 9 installed on one partition (about 1.9 GB)
Mac OS X installed on another partition (also about 1.9 GB)
(dev tools installed on OS X, too)
which leaves you lots of room to install Linux if you like.
Asking $1100 obo.