vMac - The Virtual Macintosh Emulator Project (Freeware)
http://www.vmac.org/

Emulators
http://www.freebyte.com/operatingsystems/#emulators

Operating System Solutions
Running Windows or Linux/UNIX Software on a Macintosh
and Running Mac OS on other Platforms
http://www.macwindows.com/emulator.html

Mac Emulators for PCs page
http://www.macwindows.com/macemul.html

God bless you; you know what Apple doesn't supply enough tech. reference for OS X. Just wish you have no need to write M68K/PPC assembly under Mac; for a PC guy it's a complete nightmare experience.