Multibooting on Macs?

Macler asks: "I'm new to this whole multiple OS on one machine thing.. I have been told that you can choose between 2 OS at boot up but is it possible to setup my system so that I can run Mac OS9.1, OSX and Linux on 1 harddisk and select which to run at bootup..I don't mind having to wipe the drive so any help will be gratefully recieved."