If you try a Mac magazine there are usually a few ads in the back for second hand Mac dealers: I know MacUser used to have a few advertising in the back along with the printing people: usually only a small ad. Don't forget though, that you can now buy a new G3 iBook for less than the price of a new iMac, and they are well specced (not to mention gorgeous - much nicer than the G3 PowerBook which I think is a bit slabby and overly chunky). And as far as warranty and second hand dealers go you usually only get 90 days I think.