Check link below for details:http://sixrevisions.com/usabilityaccessibility/10-promising-free-web-analytics-tools/
I think Yahoo does the best work comparing with others.
The data analyze and web data mining will be the next generation of data base revolution. MOre and more business come from Web.
Websites like http://www.ohloh.net/ are doing analysis for more detail level of industry/application. Searching by business/type of user and bring more useful data for these users are more and more important for people. Data grows like rolling snow ball, something like Google but more specific and useful is needed.
It's time to do something.