Linked to from my earlier piece on how greatness cannot be planned, the Sante Fe Institute Operating Principles (PDF) by Cormac McCarthy are short and great. Even if you don't like PDFs, this is just one page, and it's fun to see the inline corrections and to read the note in its typewriter-like typeface.
I like the ending line.
Occasionally we find that an invited guest is insane. This generally cheers us all up. We know we're on the right track.