Ballistic evidence points to all the shots coming from the depository window, and virtually all evidence points to Oswald being in that window. The shooting aspect of the conspiracy is beyond legitimate debate.
However, as John Kerry recently put it, it's still possible that Oswald was coaxed into carrying out the assassination or was a pawn in a wider conspiracy. But it's far from a slam-dunk and those questions and loose ends can be solved with the official story of him being a weirdo, to less eloquently paraphrase dirge. Is it possible there was more to the assassination than the accepted, mainstream narrative? Of course. There's just not the evidence to back it up, so believing in it is a matter of faith rather than a result of a fair analyisis of what happened.
The whole JFK conspiracy is the ur-example of Baby Boomer self-centeredness. It was a defining moment in their childhoods, so it just CAN'T be the case that the dashing young president was killed for no reason by a nut with an old rifle. It had to be an evil conspiracy carried out by the same wicked old men they would later protest against over Vietnam, which they laughably claim JFK was about to call off. Instead of a mediocre president who didn't govern as much of liberal at all, JFK had to become the martyred patron saint of American liberalism, who can get praise for being the real developer for LBJ's Great Society and civil rights achievements without having to give due credit to the racist warmonger Baby Boomers came to hate. Instead of a presidency on the brink of collapse under the weight of numerous scandals, we get Camelot and a de facto royal family.
Through tragedy, a mediocre president has been transformed into an icon. Just imagine if President Garfield had been better looking.