"Forget about it" essentially means "Don't worry about this any more," or "This statement isn't even in dispute." "Forget it" is used to accept an apology in a slightly aloof manner. Example: "Hey, man, I'm sorry I broke your tv last night," Jim said. "Forget it," I told him.

I agree with Grant. But also, in a general sense: -"to forget it" means "to not remember it." -"to forget about it" means "to not think about it" or "to not worry about it" or "to not be bothered by it" I might "forget about" the fight we had last night. But, unless I was somehow impaired, I will probably not "forget it" any time soon. As illustrated in Grant's examples, these are not strict rules, and both statements are sometimes used when the other would seem to be more appropriate.

I agree with Grant. But also, in a general sense: -"to forget it" means "to not remember it." -"to forget about it" means "to not think about it" or "to not worry about it" or "to not be bothered by it" I might "forget about" the fight we had last night. But, unless I was somehow impaired, I will probably not "forget it" any time soon. As illustrated in Grant's examples, these are not strict rules, and both statements are sometimes used when the other would seem to be more appropriate.

As it is explained by Johnny Depp, who plays Donnie Brasco in the movie "Donnie Brasco" "Forget about it" is like, if you agree with someone, you know, like "Raquel Welch is one great piece of ass, forget about it." But then, if you disagree, like "A Lincoln is better than a Cadillac? Forget about it!" you know? But then, it's also like if something's the greatest thing in the world, like minga those peppers, "forget about it." But it's also like saying "Go to hell!" too. Like, you know, like "Hey Paulie, you got a one inch pecker!" and Paulie says "Forget about it!" And then, sometimes it just means forget about it. http://www.urbandictionary.com/define.php?term=forget%20about%20it