The letters editor of The New York Times has written on the process by which letters to the editor are published and goes through a few publication guidelines. I find that fascinating, partly because I've always considered the letters to the editor page of publications as the unofficial corrections page. It's actually more than that though: it's a place where readers sound off on what they read in the paper.
Fun anectdote: The member of the British Columbia legislature for my hometown was faced legislative recall because her assistant had sent the local newspaper letters to the editor using a false name. See the second and third paragraphs of the second part of this canoe.ca column.