Here is a web site with dates: http://www.terrorism.com/calendar/Calendar.html. It's the one everyone links to.
That site is pretty extensive, including dates which are probably obscure to most people in the US and not connected with the Middle East. For some reason (unless I missed it), July 4 isn't mentioned as the US national holiday, though it is mentioned in connection with some other obscure events. You'd think there'd be terrorist significance in the great satan's birthday.