In recent days one of the things I've been working on is loadable data sets. I found a free source with ~400 business types organized into categories and subcategories, and I've added that as an option in the WSN Directory installer. I'm also using that to generate a dataset of the same categories as 3rd and 4th level subscategories beneath USA states and Canadian provinces (e.g. Canada -> Ontario -> Finance -> Insurance).

What other datasets might be useful?