No respectable scholar uses the term "The Dark Ages" anymore, and even the oft-disparaged-as-backward Early Middle Ages (roughly 300-1000) have been rehabilitated among scholars, given such innovations as creative use of wind, falling water or agricultural techniques that came about in the said period, the kind that were unknown to the Romans. Since the very notion of the Middle Ages (variously dated, but roughly from 300-1400) is a very broad term among scholars, not used in historiography until the seventeenth century (Petrarch gave birth to it only conceptually), you might want to refine your question. Are you, for example, asking about social, economic or intellectual milestones that scholars have utilized as an argument for a waning of the Middle Ages? Something else?

Here's a book recommendation to get you started: Johann Huizinga, The Autumn of the Middle Ages, (Chicago: University of Chicago Press, 1996).
I would also recommend an excellent piece of very accessible, lively, popular history that will challenge any view of the Middle Ages as "dark": Frances & Joseph Gies, Cathedral, Forge, and Waterwheel: Technology and Invention in the Middle Ages, (New York: Harper Perennial, 1995).

EDIT: Obsessive-compulsive word choice and flow corrections, additional book recommendations.

Keep in mind that The Dark Ages are not called so because they were particularly terrible or anything, but rather for the dual reasons that there weren't that many records left behind and thus it's a "dark" spot on the timeline in the sense that we can't know as much about it as we'd like to [A]. The secondary reason is because the dark ages were after the fall of Rome, which at the time was considered a period of considerable darkness [B]. The secondary meaning of the term has greatly fallen out of favor among academics because they tend to try to be rather neutral about what they study. As long as we're clear that historians refer to the Dark Ages as a period of "knowledge darkness" and not being particularly bad or unenlightened, I can go on a bit. There's also a problem of what do you mean by the Dark Ages? Sometimes when people say The Dark Ages they mean "the middle ages" or sometimes just the early middle ages (5th-10th centuries) [C]. I will try to answer both in my response.

Assuming you mean the end of the middle ages, there is no unanimously agreed upon event which we call a turning point. Typically the invention of the Printing Press (1450 or so) is used to mark the end of the medieval period but that is not used among scholars. Among historians the Renaissance (and thus the end of the dark ages) is argued to have taken place from 1300-1700 (or 1350-1600). It's a murky issue with much debate and any one event you could name could come off as arbitrary to some historian.

Notable events include: Petrarch's rediscovery of Cicero's Letters [D], Lorenzo Valla exposing the Donation of Constantine as a forgery [E], and the Rise of Scholasticism [F]

If we think of the Dark Ages as only the early middle ages the question becomes a lot tougher. What was the turning point? When did it end? I've got to admit I don't really know, as this is somewhat out of my field of knowledge: but I would say the rise of Charlemagne would be a good turning point in the sense that Charlemagne is widely regarded as spreading learning and Christianity (The Carolingian Renaissance) [G].

The last thing I'll leave you with is that it is generally frowned upon in history to "construct a narrative of progress." Usually the idea that earlier societies were shit and every important event has been them working their way to our great society is not well regarded simply because Progress means different things to different people and history has its confusing ups, downs, cycles, and exceptions. I hope I'm not disheartening you in your search for knowledge. Below I've tried to give you some light reading if you're interested in this stuff.

A - Jordan, Chester William (2004). Dictionary of the Middle Ages, Supplement 1. Verdun, Kathleen, "Medievalism" pp. 389–397.

B - http://www.jstor.org/discover/10.2307/2856364?sid=21105857578213&uid=4&uid=2&uid=3739256

C - http://en.wikipedia.org/wiki/Dark_Ages_(historiography)#cite_note-OED-1

D - http://en.wikipedia.org/wiki/Petrarch (wikipedia article on Petrarch) http://petrarch.petersadlon.com/timeline.html (timeline of Petrarch's life)

E - http://en.wikipedia.org/wiki/Donation_of_Constantine (Donation of Constantine), http://en.wikipedia.org/wiki/Lorenzo_Valla (Lorenzo Valla)

F - http://en.wikipedia.org/wiki/Scholasticism

G - http://en.wikipedia.org/wiki/Charlemagne (Charlemagne), http://en.wikipedia.org/wiki/Carolingian_Renaissance (Carolingiang Renaissance)