Kaf has written some nice code to split a post into two columns:
<?php $content = split("<!--nextcolumn-->", $post->post_content); ?>
To use this, I add <!--nextcolumn--> into the post where I want the next column to start.
Would it be possible to create a customised 'Write Post' page, that actually displayed these columns in 2 distinct text areas? (For the benefit of a client.)
Pages with one column would revert to the default editing layout of course.
I'm more of a hack&paster than a coder but would be interested to hear your thoughts on tackling the above :-)