From Wikipedia: - Illuminati (plural of Latin illuminatus, "enlightened") is a name that refers to several groups, both historical and modern, and both real and fictitious. Historically, it refers specifically to the Bavarian Illuminati, an Enlightenment-era secret society founded on May 1, 1776. In modern times it is also used to refer to a purported conspiratorial organization which acts as a shadowy "power behind the throne", allegedly controlling world affairs through present day governments and corporations usually as a modern incarnation or continuation of the Bavarian Illuminati. In this context, Illuminati is often used in reference to a New World Order. Many conspiracy theorists believe the Illuminati are the masterminds behind events that will lead to the establishment of such a New World Order.
From Jeffy's Head: - The Illuminati would be an organization of Artisans and Scientists who would like to lead the world to embrace the arts and sciences as the highest pinnacle of man's experience - and in doing so would do away with petty human trifles which cause anguish, grief and all human suffering (up to and including needless death) caused by bureaucracies and organized religion. Up with the enlightened, down with the ignorant time and life wasters, say I!
From Jeffy's Head Addendum: - In my mind the Illuminati would include membership by such art and science minded people as Stephen Hawking, Willie Nelson, Steve Jobs and Jerry Beck. Ryan Seacrest may or may not be a member, but if he is, he was "kissed in" by a former member, much the same way he gets to host "Rockin' New Years Eve".