Stable URIs: If you've got a large data set with real objects in it, don't just display them incidentally thru some other interface -- give them web pages with stable URIs. Then they'll show up in Google, get linked to by other people, all sorts of good stuff.

Visualizing Data: A book by Ben Fry that covers programming dynamic visualizations of large data sets. Covers everything from scraping the data to writing your own graph libraries to display it. Provides an introduction to the Processing language as well.