Macintosh
One of the common definitions of "retrocomputing" is "more than 10 years old", such as used by the http://classiccmp.org mailing list. For Macs, that happens to pretty much perfectly fit the line of "Old World" / "New World". That is, pre-iMac and post-iMac. Of interest to hobbyists includes, especially, the compact Macs and the Mac II line, though as time goes on, early PowerPC Macs may qualify as "historical computing". Early Macs are certainly often the first computers many younger people today encountered and have great sentimental value for many people.
Contents
Systems
Compact Macs
Macintosh II
The Macintosh II series...
MacOS
Classic 68k and PowerPC Macs are notable not so much for their hardware (though they tended to be more sophisticated and use higher-end components than other personal computers of their eras), but their for their operating system, MacOS, Macintosh System Software... it goes by a few names.
Emulation
Today, both 68k and PowerPC macs, as well as right up to the latest versions of OS X are all emulate-able, with varying degrees of ease. We'll concentrate on emulating "old world" Power PC and Motorola 68k based Macs here.
Basilisk II
Basilisk II is the de facto official emulator of the MacOS 68k environment. It's important to note that the emulator is highly customized toward running MacOS inside it, and will not handle AU/X or modern UNIXes written for 68k Macs. See the Wikipedia article for more information. Guides and compatibility tables and so on will be posted here later.
http://en.wikipedia.org/wiki/Basilisk_II