There exist hundreds of web analytics software to help you understand how people discovered your website, how long they stayed on some web page, what browser they were using, etc.
Whos.Amung.Us takes a different approach to web stats and answers two very useful questions in a visual manner. The questions are:
(a) How many people are currently on your blog ?
(b) What stories of your blog are they reading at the moment?
whos.amung.us is not about pageviews or organic search keywords, it's about visualizing content that is being read by visitors on your blog this very moment.
Like the del.icio.us tag cloud, this service will also show a list of your most popular blog pages - the larger the font, the more hits or more people reading that page.