Audience measurement services

I'm trying out alternatives for Google Analytics
So I've found a valuable contestant, let's wait and see: Quantcast is the World’s Only Open Internet Ratings Service

Quantcast is a new media measurement service that lets advertisers view audience reports on millions of websites and services. Only Quantcast combines directly measured audience data with panel-based estimates to deliver accurate third-party metrics and easy-to-read profiles on digital media properties.

Advertisers – Find an Audience!
View detailed audience reports for millions of websites and services to find the audiences you seek and build your brand online with confidence.

Publishers – Make Your Audience Count!
Demonstrate the unique value of your audiences and attract advertisers by tagging your websites, videos, widgets and games for direct measurement.