As of today, Harper's Index is free online. For those of you who might not know, Harper's Index is a collection of information set out in single lines as if it were statistical data and in a way that is meant to surprise and interest you. In the online Index you're presented with a search box — which will return helpful suggestions as you type, guiding you to those terms that do in fact appear within the index.
For example, a search for "law" produces over half a dozen screenfuls of items, the first of which is:
The first numbers tell you which issue of the magazine the stat first appeared in, and the link will take you to the index from that month and year. The hotlinks in the statement act as search terms so you can roam through the index from term to term. And the link underneath takes you to the source. These links and the source, which is usually named in full, will appear AJAXily, when you mouse over an Index item.
Beautifully done, clearly fun — and possibly useful. Which ain't bad in a resource.