some tid bits i've learned off are:

The Secret Service took a bunch of video camera from people video taping that day.

There were some guys with umbrella during a sunny day in the grassy knoll. They were coching the umbrella like shot guns (apparently).

Since then spectators aren't allowed to have umbrella's near the president (i dunno about that one either).

Either way, tons of theories on that one.

I've heard Kennedy wanted to pull out of vietnam and that was one reason why the government may of assassinated him.

Who knows...