I read a book called "Contract on America - the Mafia Murder of JFK". By the time I finished it I was convinced it was arranged by Sam Giancana. It lists all kinds of evidence that is really convincing.

I just recently saw the movie the details the Joseph Bonanno story, and in it there is a scene where a sniper is in the sewer facing JFK's limo as it heads toward him.

It seems to easy to say it was Oswald. there are so many interesting sidebars to the story - the "tramps" that were photographed as they were arrested but no record of the arrest was ever found, or the unusual number of mysterious deaths of the witnesses that were in Dallas that day. Or the truly magic bullet theory. All interesting stuff, and all gives rise to a number of theories.