There are some of webanalytics software to help you understand how people discovered your website, which pages they like, how long they stayed on web pages…
Whos.Amung.Us has a different approach to webstats and answers 2 very useful questions :
1) How many people are currently on your blog ?
2) What stories of your blog are they reading at the moment ?
As for me, the second question is the most important. Whos.amung.us doesn’t work with keywords search or pageview. Actually, it visualizes contents that is being read by visitors on your blog in every moment.