Regarding the JFK assassination, as long ago as 1966, U.S. left filmmaker Emile de Antonio's Rush To Judgement movie provided evidence that the Warren Commission case against Oswald is deeply flawed. Claudia Furiati's book ZR Rifle: The Plot To Kill Kennedy and Castro is one of many that also provide evidence of a JFK assassination conspiracy. In the words of this book's back jacket: "Supported by extensive use of Cuban State Security Department materials, Brazilian journalist and film-maker Claudia Furiati shows how and why the CIA, through those responsible for its anti-Cuba operations, along with anti-Castro exiles and the Mafia, planned and orchestrated the Kennedy assassination."
Regarding the 9/11 events, the evidence cited on web sites like www.globalresearch.ca, for instance, rarely gets discussed freely in those parts of the alternative media in which the U.S. left "conspiracy-denialists" are still influential.
bob