In the recent past, has there ever been a Conspiracy Theory that when it was all said and done, it turned out to have been true, there was a conspiracy and it was exposed.
It depends what you mean by "conspiracy theory". Take Watergate, for example. There was a real conspiracy there. Woodward and Bernstein had a theory that this conspiracy was there, and upon investigation their conspiracy theory was shown to be true. There was a conspiracy, and it was exposed.
COINTELPRO, the way Gazpacho described it upthread is another good example: People theorized that the FBI was conspiring against them. It turns out their conspiracy theory was true. There was a conspiracy, and it was exposed.
So that's one meaning of "conspiracy theory". Someone has a theory about a conspiracy. They investigate, find evidence, and expose the conspiracy. Is that what you mean by "conspiracy theory", GregHouseMD? If so, then yes: conspiracy theories are proven to be true all the time.
Any time the police bust a smuggling ring, that's a conspiracy theory that was in fact true. Any time a citizen's watchdog group uncovers corruption at City Hall, that's a conspiracy theory that was in fact true. But in practice, nobody ever refers to these kinds of investigations as "conspiracy theories".
Instead, the term "conspiracy theory" usually refers to a certain kind of ignorance-based magical thinking that rejects contrary evidence and that multiplies entities unnecessarily.
So that's the other meaning of "conspiracy theory". Someone is engaging in profoundly flawed thinking, the kind of thinking that almost never finds the truth, because it actively rejects the truth. Is that what you mean by "conspiracy theory"? If so, then no: conspiracy theories are almost never true, for the same reason lies are almost never true: The terms identify things that are by definition untrue.