Scott over at the Acronym blog posted an interesting idea: The Mystery Shop. I remember way back when when I worked in a convenience store, and the rumor was that corporate would send in someone to check out what we did and report back on it. Having a permanently guilty conscience, I always worried that the one time I hadn't restocked the milk, that would be when the mystery shopper would come in.
That said, I do think it'd be a great idea to bring in someone who's unfamiliar with your organization and/or your meeting to check it out with a pair of fresh eyes. It reminds me of this post about inviting some kids to come to your meeting, videotape it, and critique it. I still love that idea, but I guess grown-ups would work as well. They probably wouldn't be as forthright, though.