The Mac Plus is one of my favorite Macs. It finally resolved many problems the were in the Macintosh platform upon its birth. Released in January of 1986 for $2600, 2 years after the first Mac, the first Mac to ship with an entire megabyte of memory (not counting Mac XL) was released. Now greatly surpassing the Lisa and Lisa 2 in speed, memory, and reliability, the Mac Plus finally allowed memory intensive applications to be run easily on the machine. With its double-sided 800k disk drive, and a SCSI port for an extra hard drive, Mac users believed space would never be a problem again. Also, the Mac Plus finally allowed efficient desktop publishing to begin, and with applications like PageMaker, the Mac was secured a place in the computer industry.Among the problems addressed by the Mac Plus was an extended keyboard which was lusted by many Mac users of the time, sufficient memory, larger ROM (twice as large as original Mac), and a SCSI port for expansion. The versatility of this machine is so great, that it stayed on Apple's product line longer than any other machine, almost five years. Even today, thousands of Mac Pluses are used in schools, businesses, and homes (I'd like to get one myself!). Steve Wozniak, who was awarded the 1 millionth Macintosh shipped (a Mac Plus) still uses it in his office along with his PowerBook 180. You can even see a Mac Plus in the movie Star Trek IV: The Journey Home (my personal favorite in the series) where Scotty uses it to create a new kind of industrial-strength plastic. There have even been articles and discussion groups that find new ways to keep this little machine alive. It's just another one of Apple's great little beige boxes.

Code Names: Mr. T, maybe from "The A Team" series, or Apple's chief scientist Larry Tesler who had the same nickname.

Specifications:
Processor: Motorola 68000 processor running at 8 MHz (same as Mac 128k).
Memory: included 1 MB of RAM, 128k ROM
Drives: a Sony 800k 3.5" drive.
Display: built-in 9-inch diagonal, 512 by 342-pixel monochrome bitmapped display.
Ports: mouse port, one eight-bit keyboard bus, 300 baud, RJ11 connector for the Macintosh Plus Keyboard. Two RS-232/RS-422 serial ports, 230.4K baud maximum, Mini DIN-8, and sound port for external audio amplifier or headphones.

Operating Systems:
Mac OS: came with System 3.2, supports versions System 1.1-7.01, 7.1, 7.5-7.51, 7.53-7.55. System 4.3 is reccomended.

Interesting Facts:
Again, I wasted my interesting fact in the description at top. In mid-1986, Apple finally shipped its 1 millionth Macintosh, appropriately a Mac Plus. Six of these were deemed "The 1 millionth Macintosh" and one of them was given to Steve Wozniak. It is still used today along with his other Macs.

If you hit the interrupt switch on any Mac Plus, and type the string "G 40E118" without parenthesis, you'll get the prompt "Stolen from Apple Computer". You might wonder why it does that though. It was common practice to include this on every Mac and Apple II ROM. That way if the ROM was used illegally (as it was often) you could enter this string and find out if it was stolen or not. Fairly interesting trivia you can tell your Mac-addicted friends ;)

Resources and Related Links:
Apple's Technical Information Library
David Pogue's and Joseph Schorr's Macworld Mac SECRETS.
Picture above from Sun Remarketing.