Rand at Seomoz.org provides with an impressive and exhaustive list of statistics of several websites. The list is an excellent resource to collect statistical data on various websites. He writes: "I've attempted to lay the foundation for every piece of website data available to marketers, researchers and the curious."
The tools are categorized into following heads: Technical, Ownership/Hosting, Statistics/Popularity, Search Engine Indexing, Link Data, Social Tagging, Third-Party Trust Metrics, Important Directory & Site Listings, Press & Media Mentions.
Here are few examples from the list:
IP Address – via DomainTools Search
Whois Data (registrant, registration date, contacts, etc.) – via DomainTools Search
Search Engine Indexing Data:
Google's Indexed Pages – via Google site: command
Yahoo! Link Data – via Yahoo! Site Explorer
Third-Party Trust Metrics:
TrustGauge Rank – via TrustGauge
Important Directory & Site Listings:
Listings in Wikipedia – via Wikipedia Search