Our tool set handles navigation and hierarchical categories by using a simple database record for each category.  Each category record contains an ID value, a "Short Title" and a "Long Title". The short title is used as the categories name within the left hand menu area where space is at a premium. The long title is used primarily as a tool tip so that when someone holds the mouse over a menu item they can see a more complete description of the category item. 

Each category has at least one define parent that it will be listed under. The main categories you see now on the left all have a parent value of "0", meaning that they nest under the HOME page. But the database structure allows any category to have multiple parents. This allows any category and it's children to exist in more than one place at a time.

More detail about this topic is available on the main website.