What to say when the other person is talking and you know they're full of crap

I was with friends in New York recently, and this subject came up. My buddy, Dave, told me how he used to say, "You might be right", to some senior citizen friends of his when he knew they were completely off in left field somewhere. He didn't want to offend them, but he wanted to say something, and if he could make it sound like a compliment, even better. During the weekend we all came up with a few more useful exclaimations to be used in the same situations. Remember now, the other person must be saying something that you know to be absolutely false, but you don't necessarily wish to offend them by correcting them.

"You might be right"

"Really" (With vigor. Like you're giving them a chance to take it back.)

"I didn't know that"

"That's interesting"

"Huh!" (With the tone of mild amazement can be used in conjunction with any of the others. It's an exclamation, not a question.)

"I hadn't heard that before just now"

I've got a bunch of them, I just can't think of them all right now. If you want to add some, just send them in a comment.