expandable list of pages displayed in a sidebar widget — now to

Howdy Folks,

I’m fairly new to using wordpress as a CMS, though I’ve run a basic blog with it for a while now.

I need to create a number of pages on a particular site, each for a different business that will reside in a “directory.” This directory will be nothing more than a collection of the individual pages for the particular businesses. Each page will belong to a category, such as “Salon” or “Restaurant” or “Clothing.”

I’d like to display the list of the businesses, preferably in a sidebar widget, in such as way as the user would expand the category to view a list of links to the individual pages.

What’s the best way to approach this task?

Bonus Question: what’s the best way to make a fully expanded view of the “directory” available on one page?

Thanks!