I too am a member of the Ohio Less Wrong group. I was quite surprised to see this topic come up in Discussion, but I approve wholeheartedly.

My thoughts on the subject are leaning heavily towards the current equivalent of an 'elevator pitch' we have already: the Welcome to Less Wrong piece on the front page.

I particularly like the portion right at the beginning, because it grabs onto the central reason for wanting to be rational in the first place. Start with the absolute basics for something like an elevator pitch, if you ask me.

Thinking and deciding are central to our daily lives. The Less Wrong community aims to gain expertise in how human brains think and decide, so that we can do so more successfully.

I might cut out the part about 'human brains' though. Talk like that tends to encourage folks to peg you as a nerd right away, and 'nerd' has baggage you don't want if you're introducing an average person.