Recently had a client that wanted to customize the layout for a category landing page so that the category's title and description would be displayed above the layered navigation and product grid — essentially creating a full-width section above the left sidebar and main content areas.
NOTE: For reference, this is based off the blog post from Collaboration133.com's Magento - Add Custom Structural Block Reference.
I created a custom module to help organize and identify that there are some custom modifications to layout templates. Not saying you have to, but it may be easier for other's (or your future self) to recognize and find what customizations were done (and hopefully why).