Regarding the Societal Ramifications of the Enlightenment
Through all of the lengthy pontificating of the enlightenment philosophers, divergent as their trains of thought might be, there was a single uniting common thread: the desire to better humanity through understanding. The interaction between the different philosophers in regards to the "true" nature of the understanding and the manner in which it would better humanity was almost comic. Bentham insisted happiness was the key, Rousseau insisted on denial of "reality", Locke on direct interaction with reality. The "exchange" of ideas that embodied the period was, in actuality, more like countless strands of individual trains of thought, constantly contradicting each other, and yet they are all lumped together as "Enlightened Thinkers" for a reason. Were it not for them, our current social, educational, philosophical, and political thought simply would not be.
Diversity was perhaps one of the greatest strengths of the enlightenment philosophers. Virtually every form of government that has been conceived since the enlightenment period has its origin in their lengthy discourses on the issue. From Rousseau stems communism (the political system, not the economic system), "enlightened anarchy", and fascism, an array of which the honor of having birthed is somewhat dubious, though not without its redeeming aspects. From Bentham's Principle of Utility, we have the concept of direct democracy, and so by extension all permutations and bastardizations thereof. In Voltaire's work we find the principled underpinnings of the "free world". Though the effectiveness and viability of these governmental forms is subject to heated debate, they are at least something other than absolute monarchy which, along with anarchy, was one of the two primary governmental systems that had existed prior to the political diaspora of the late renaissance.
In the wake of the vast evolution of politics, human social systems in the affected continents were presented with a unique opportunity to restructure themselves. Not to imply a conscious force behind the social restructuring, but many of the concepts that entered into the periphery of the public view at this point had their roots in the philosophies of Rousseau, Diderot, Voltaire, and Bentham. The issues of human rights, particularly of the inalienable sort, became something of a focus at this point in history, and over the last couple centuries have remained the focus of significant speculation. Most notably in contemporary politics in the issue of affirmative action, societies must decide to what extent the interests of the demographic majority should be allowed to supercede or impede the interests and rights of the minority, and to what extent the ideal should be allowed to dictate perceptions.
The basic nature of information, particularly in regards to its communication, was radically changed by the thinkers of the enlightenment. Both Diderot and Voltaire were advocates of free speech. Diderot's purpose in the Encyclopédie is now not only shared by virtually every would-be historian and scholar, but it is also the fundamental principle of the internet (particularly this site). Free expression and exchange of ideas is certainly not universal in today's society (John Ashcroft, for example, stands stolidly against it), but it has remained in the social mainstream since their time, and had not really been seen before that except in ancient Greece and Rome, so the Enlightened Thinkers deserve at least some credit for this.
Even the more misguided of these prolific philosophers, such as Locke or Rousseau, have had a lasting impact on philosophical thought. Newer philosophic traditions tend to describe themselves by the older philosophies which they most resemble. Though this may not seem like a very notable influence, one must bear in mind that by serving as something of "component parts" to newer philosophies, they tend to shape to direction in which that philosophy drifts. This concept of gradual shaping very well represents the sum influence of the enlightenment philosophers on today's social, intellectual, and political condition: Aside from the push that spawned the initial products of the enlightenment, their ideas have, by a slow and gradual process influenced by all who came before and after, moved towards the place where we find them today, and will continue to guide us into the unknown realm of the future.