From a 2 column to a 3 column.
I have just found a great article on changing your wordpress theme from a 2 column layout to a 3 column layout. Claire Campbell wrote the article.
It explains in relative layman's terms on how to change the CSS stylesheet and a bit HTML jiggery pokery to get your 3 column layout.
The explanation on DIV tags was particularly helpful and it got my head around DIVs which I have been trying for a while.
If you are interested at all in changing the layout or learning a bit more about the makeup of a wordpress theme why not read the full article here