"ClickHeat is a visual heat map of clicks on a HTML page, showing hot and cold click zones.", reads the description on the front page. For more details on how it works click "Demonstration" and use demo/demo for log in and password. Take a look at the image below to get an idea how the heat maps generated by ClickHeat look like.
I think that this application is extremely useful for webmasters and librarians to find out where are the "hot" zones of the library websites, blogs or wikis and maybe rearrange sections of the pages and layout to increase the number of hits and visits.