Here's a build of Executor for OS X:
http://www.emaculation.com/executor/Executor.app-20091029.dmg
Executor is an emulator that does not require a ROM. It runs many System 6 era programs, and some SSW 7 era stuff too!
I read all about it on MacScene:
http://macscene.net/forums/viewtopic.php?f=6&t=659
Edit: Replaced 'xxx 7' with 'SSW 7' - IIGS User