Yay, it happened again!  I was reading an article from The Economist -  Grokking the infoviz., Economist, 00130613, 6/21/2003,  Vol. 367,  Issue 8329 about visual mapping, and while it mentioned Grokker and Antarctica, what really turned me on was a mention of something called hotmaps, and there's one to see at http://www.smartmoney.com - use the MAPS pulldown.  This is based on something called TreeMap, which apparently I can play with for free - I really want to figure out how this could be applied in a library setting...

So I'm pumped about the world of information again :-)