Former former Pentagon intelligence analyst Ted Van Dyk has an interesting article here on the JFK assassination.

As a former Pentagon intelligence analyst, I was delivering a lecture at the Defense Intelligence School to a group of career military officers from all branches of the service. Midway through my lecture, a Navy captain entered the room, moved me aside at the podium, and announced the following: "President Kennedy, Vice President Johnson, and Texas Governor Connally all have been shot and killed in Dallas. Stand by for further information."

There were a host of other unanswered questions: The CIA, during the period, was sending supposed "defectors" into the USSR to gather intelligence. Was Oswald one of them? Or was he, in fact, a genuine Soviet asset? As a Marine, he had been stationed at a highly classified facility that monitored CIA spy-plane flights over the Soviet Union.

For whatever it is worth, my best guess is that a rogue CIA/mob group planned and engineered the assassination, setting up Oswald for blame. He was a part of it but, perhaps, only as "the patsy" he said he was.

Update: I made an email inquiry to the author regarding the "defector" program. His reply:

I was an intelligence analyst for 7 1/2 years, mostly as a Reservist,and then assistant to Sen. and VP Humphrey for five years and, later, a State Department official. I had general knowledge during that entire period of a defector program---although no specific knowledge. The Soviets were known to have their own counterpartdefector program, sending agents into the West. There was always deep suspicion when a supposed "important" defector came West. Oswald would have been seen as small fry, both by us and the Soviets, and of no particular importance. It is conceivable that he worked both ways.