Pretty much agreed with most of you re: the conspiracies (Russ is eerily close to my train of thought on Kennedy and Area 51).
JFK, MLK, and RFK: Yeah, I'd say there were lots of unanswered questions for all three. Those three were very threatening to the status quo in one form or another, and the fact that their assassinations came in somewhat quick succession is very telling. We'll likely never know the whole truth on any of 'em, though.
Area 51: I'm sure that the US gov't has found something extraterrestrial and covered it up, but like Russ said, Area 51 is the very public decoy, diverting attention from the real unmarked places the military has throughout the country (Most of those secret bases are mainly for prototype/new weapons testing - Area 51 was where the Lockheed Have Blue program was conducted - this was the development of the prototype of the F-117 Nighthawk stealth fighter).
9/11: IMHO there was no conspiracy, apart the one from the 19 terrorists. No controlled explosions, etc. It happened like we all saw it. I'd read, however, that there were some red flags from some of the pilot training centers where the terrorists who piloted the planes attended in the US that were ignored by the various security agencies, but that's hindsight. Nobody really could have anticipated this happening, and it served as one hell of a wake-up call for everyone.
Elvis: is out there, somewhere, fighting crime. With Bruce Lee. TCB.
"It's sad that governments are chiefed by the double tongues. There is iron in your words of death for all Comanche to see, and so there is iron in your words of life. No signed paper can hold the iron. It must come from men. The words of Ten Bears carries the same iron of life and death. It is good that warriors such as we meet in the struggle of life... or death. It shall be life."