How to Write Documentation
I think this may be one of the best 'how to write documentation' articles I've ever seen, especially with the examples in the link at the bottom. I'd love to see more examples like that in these sorts of tutorial.
Master Terafan Greydragon's "Documentation is not an Obituary".
Found through the Atlantian MOAS links site, which I got to from a link to "Documentation Is Not A Dirty Word" by strawberrykaren on a post by a friend.
It's always keen to find that someone else has already done the thing you were thinking should be written. ;)