SFAC3: Zebulon's Guide to Frontier Space, Volume 1
Zebulon's Guide to Frontier Space was a supplement/rules update for TSR's early-1980's science-fiction RPG Star Frontiers. The name is obviously a take-off on Douglas Adams' Hitchhiker's Guide to the Galaxy. Star Frontiers veterans may remember that Zebulon is the star system where the initial Volturnus series of modules took place (SF0-SF2).
Zeb's Guide was published by TSR as the last official Star Frontiers product, ever. Originally, plans were made for a series of 32-page supplements, similar to D&D's Gazeteer series, with each supplement dealing with a specific topic, like robots, cybernetics and bionics, new alien races, new starships and space combat rules, etc., hence the "Volume 1" in the title.
Unfortunately, TSR dropped the Star Frontiers line in favor of the ill-fated Buck Rogers in the 25th Century franchise (it was rumored that the TSR exec responsible for this decision stood to gain tons of royalty payments, as she was a granddaughter of the original Buck Rogers author). Everything the SF team had been working on was stuffed into one 64-page book, and the whole shebang shoved out the door into the waiting hands of SF gamers, who had gone years before seeing any new official material.
The result was a hodgepodge of new campaign background, new items, four new races, streamlined combat rules, an expanded skill system (with over a hundred skills) and a replacement for the old percentile resolution system in the form of a four-color Action Resolution Table (almost exactly the same as that found in the Gamma World 3rd edition rules). To this day, the Zebs vs. AD (Alpha Dawn, the original system) debate still occasionally erupts on the Star Frontiers mailing list.
Attempts have been made by the fan base to marry the two incompatible systems, with mixed results (the latest is the SF2000 system). Most game referees use the base Alpha Dawn system, and pick and choose items and campaign material from Zebs.
There is only so much you can put in a 64-page book, though, and a lot of material still got cut. The cyborg rules reportedly surfaced in a 3rd edition Gamma World module, Epsilon Cyborgs, while the powered armor rules were published in Dragon issue #129, Armored and Dangerous by David Dennis. Apart from several other Dragon articles, no other official Star Frontiers material has been published since.
Most details from mailing list scuttlebutt and from my dog-eared copy of Zeb's Guide.