Apple old tech

I'm considering getting a PowerBook G4 however, I want to find one for pocket change ($60 or $70 maximum) that runs OSX Leopard. Any ideas, blog readers and friends? I've taken quite the interest in Apple's old eMacs, PowerBooks and Iphone 2G/3Gs (not 3GSs, the s is meant to make it plural). I think that old technology from a great company can never be truely outdated and can always be repurposed or refurbished when broken down. :)