I have always wondered how to get an extra column into wp. I normally just call the sidebar and footer from index.php as usual and then if I want a three column layout, put the two columns in the sidebar. e.g.
[/div][!-- end of id content--]
[/div][!--end of id wrapper--]
In the sidebar.php I have two divs, one called leftcol and float this left and the second say rightcol and float it right. (It is a little bit more complicated than that but for ease this is how I will leave it).
Now we finish the index.php by telling it to call the footer:
This is easy to implement but not very efficient. So how about this:
However, if I add this line after the call to the sidebar:
include (TEMPLATEPATH . '/extra.php');
Then I can add an extra column without resorting to having in sidebar.php.
Why is this important? Well maybe the opening page is a three column layout which upon opening a post goes to a two column structure. Using the above will help that process.
By the way I have changed the <> brackets for  just so it doesn’t break the site.
Thanks for reading.