The RPGA (previously called the Role-Playing Game Association, the Role-Playing Gamers Association, and the RPGA Network), was part of the organized play arm of Wizards of the Coast which organizes and sanctions role-playing games worldwide, principally under the d20 system. The group was founded in November 1980 by Frank Mentzer of TSR, Inc., the original publishers of the Dungeons and Dragons game. It was created to promote quality role-playing and to allow fans of role-playing games to meet and play games with each other. For most of the RPGA history all game systems were supported to some degree but current focus is solely on the Fourth Edition of Dungeons and Dragons.
The RPGA since the premiere of the Fourth Edition of Dungeons and Dragons has been slowly shutdown and the remaining elements were rebranded as D&D Events under the new Wizard's Play Network around the time of GenCon 2009 this year.
Information:
Brief Summary of RPGA Network.
Current homepage of the "RPGA" also known as D&D Events
Previous official homepage of the RPGA (now mostly empty).