Check out a cool little application called MacTracker – it is very useful for people that support Macs for a living. Both OS 9 and OS X versions are available.

Mactracker provides detailed information on every Apple Macintosh ever made, including items such as processor speed, memory, upgrade, and expansion options. Also included is information on Apple monitors, printers, scanners, digital cameras, iPod, Newtons and versions of the Mac OS.