The one-page Netrunner Rulebook
The Rulebook was printed in 1996, and quite a number of rulings have been made since then. While most CCGs have reprints of the basic cardset that update the rulebook and card wordings, Netrunner has not been so fortunate, and the rulings contain a number of errata listings, clarifications, and minor rules changes. Currently, the rulings are maintained by Holger Janssen (Rules Sensei for the Top Runners Conference) and are available here.
i created the first virtual expansion for Netrunner, which is sort of like being the first person to fall in a mud puddle—notable (perhaps) but not for the reasons you'd like to think.