Terry, we yell corrections at the TV in our house, too. In fact, I have both of my kids trained to call out, "Well!", whenever they hear "You did so good" (or the like) on television. And we hear it constantly!
(Of course, the amusing if slightly awkward part is since they are so used to correcting it on TV, they'll automatically correct adults in person who do the same. Heh.)
Spelling-wise, though, I'd have to say my number one pet peeve is the it's/its distinction. I tell my kids that if they learn to properly use "its" as a possessive, they are up on 99% of adults in this country. My favorite (not) is when people will actually argue with you that "it's" must be the possessive because it has an apostrophe. To that, I just remind them that "his" and "hers" don't have apostrophes and they are, in fact, possessives.
Kathy
