I've always wanted to randomly mail letters to strangers and see what type (if any) of responses I get. But, I, too, am lacking balls to do that. Well, not to do it, but to put my return address on it.
I think it would be fun to walk around and find a cool house, and then write an anonymous letter to the owner telling him/her why I like the house so much. I would worry that they would get freaked out, though, and think I'm an arsonist, or a burglar, or whatever.