We are at issue 6 already! In this issue I have linked to several things that have come out of the Paris face to face meeting of the CSS WG. Those meeting notes can be a bit tough to read, but if you are interested in emerging specifications for layout there is useful information to be found about how specs are developing.
In all of this new stuff there is a huge amount of scope for good explanations and tutorials to be written. If you write something about CSS Layout let me know the link, as I would love to include it here!