Hitwise

Hitwise, an Experian Company, billing their service as "Using the world's largest internet user sample to connect marketers to their online consumer", provides daily "Hitwise rankings" of the world's most popular web sites. It also monitors web surfer activity including profiling, charting and searching data from a large number of websites.

From the web site:

Each day, Hitwise provides insights on how 10 million US Internet users interact with more than 1 million websites, across 165+ industries.

A number of other products and services are also provided, including:
- Hitwise Search Intelligence™
- Hitwise Clickstream
- Hitwise Industry Statistics
- Hitwise Lifestyle
- Hitwise Conversions
- Hitwise Demographics
- Hitwise Charting
- Hitwise Ranking Alerts
- Hitwise Dashboards
- Hitwise Custom Reports
- Hitwise University

Visit Experian Hitwise