PACmeter - Popularity, Authority, Credibility Online: How To Measure Them? - Robin Good' Sharewood Tidings
Metrics Market - Internet Statistics Research and Search Engine Marketing tools
Who's Counting Clicks, and How - BusinessWeek Online - MSNBC.com
Who's Counting Clicks, and How - BusinessWeek Online - MSNBC.com
Quantcast - Open Internet Ratings Service