I think that Thomas Miconi's writeup here is the definitive one, and leaves little else to say on the matter. However, the following writeups perpetuate a few common misconectptions:

  1. You can't make an omlette without breaking some eggs
    In a revolution everyone fights. Perhaps. But at least they fight voluntarily. Those civillians who do die, do so accidentally.
    However in terrorism, the killing of civillians is precisely the intention of the perpetrators. It is a hostage situation where the terrorists threaten to kill more innocent men, women and children until their demands are met. There is never any attempt to fight toe-to-toe with the enemy, terrorists just strike in the night when they can never be hit back themselves.

  2. History is written by the winners
    It is true that the perception of events is altered by whoever actually comes out of it the best. However this doesn't change what is absolutely wrong and what is absolutely right.
    Just because the American government claims that the Contras are freedom fighters doesn't make it so. Equally, just because the word freedom fighter is associated with groups like the Contras or the IRA, it doesn't mean that the boundarys between resisitance and terrorism are forever blurred.
There is a lot of hypocrisy and a hopeless lack of clarity about who are the good guys and the bad guys. But there is a basic morality behind all things which can never be distorted.