Catakig is an emulator for the popular Apple II series of personal computers, supporting the Apple ][, ][+, //e, and //c models. The current version runs on PowerPC Macintoshes under MacOS X 10.3 and later, and on Intel Macs under MacOS X 10.4 and later.
KEGS is an Apple IIgs emulator originally developed for HP-UX. It uses SDL and is a port to the Cocoa environment.
Mini vMac emulates a Macintosh Plus, one of the earliest of Macintosh computers, sold between 1986 and 1990. It can run old Macintosh software that otherwise couldn't be used on recent machines, and so helps to preserve history, from the era when the modern user interface for computers was being defined.
Quick and Dirty Apricot Emulator
QDAE is an emulator supporting various 16-bit computers made by Apricot in the 1980s. These were non-IBM-compatible systems running custom versions of MS-DOS or CP/M.