What Can You Find Out About A Site?

I’ll repeat it here for simplicity…
Technical Data

IP Address - via DomainTools Search
(e.g. SEOmoz - 204.15.225.178)
Other Sites on an IP Address - via IP Query at Live.com
(e.g. SEOmoz’s - 204.15.225.178)
Server Type - via DomainTools Search
(e.g. SEOmoz - Apache)
Response Time - via DomainTools Search
(e.g. SEOmoz - 5.78ms)
Name Server - via DomainTools Search
(e.g. SEOmoz - dns1.dedicatedns.com)
W3C Validation - via W3C Markup Validator
(e.g. SEOmoz - we passed!)
CSS Validation - via W3C CSS Validator
(e.g. SEOmoz - validates)
Speed Report - via WebsiteOptimization.com
(e.g. SEOmoz, 23.44 seconds @ 56K - sadly, you can’t link directly to these)
Use of Text - via Ranks.nl KW Density Checker
(e.g. SEOmoz’s homepage has 662 total words, 336 uniques and “seo” is the most common, again you can’t link directly to these pages; note - I’m not endorsing KW Density; I just appreciate their tool)
HTTP Headers Response - via Web Sniffer
(e.g. SEOmoz - 200 OK)

Ownership/Hosting Data

Whois Data (registrant, registration date, contacts, etc.) - via DomainTools Search
(e.g. SEOmoz)
Additional Sites Owned/Registered - via DomainTools Search and Alexa
(e.g. SEOmoz @ DomainTools & SEOmoz @ Alexa)
SSL Certificates Issued - via DomainTools Search
IP History - via DomainTools Search
Hosting History - via Netcraft
Whois History - via DomainTools Search
(e.g. SEOmoz)

Statistics/Popularity Data

Alexa Rank - via Alexa
(e.g. SEOmoz @ Alexa - 864th most popular site)
Alexa Reach - via Alexa
(e.g. SEOmoz @ Alexa - 1395 per million users)
Alexa Page Views Estimate - via Alexa
(e.g. SEOmoz @ Alexa - 2.7 per user)
Google Trends Data - via Google Trends
(e.g. SEOmoz - no data; only available for highly searched-for domains)
Compete Snapshot - via Compete.com
(e.g. SEOmoz - 5854 visitors in August, ranked #204,215th most popular site; no direct linking in)
Ranking.com Rank - via Ranking.com
(e.g. SEOmoz - 26,741st most popular site)
Netcraft Ranking - via Netcraft
(e.g. SEOmoz - 20,319th most popular site)
Bloglines Subscribers - via Bloglines Feed Search
(e.g. SEOmoz - 448 subscribers)

Search Engine Indexing Data

Google’s Indexed Pages - via Google site: command
(e.g. SEOmoz - 18,400 pages)
Yahoo! Pages Indexed - via Yahoo! Site Explorer
(e.g. SEOmoz - 5,432 pages)
MSN Pages Indexed - via Live.com site: command
(e.g. SEOmoz - 11,416 pages)
Ask.com Pages Indexed - via Ask
(e.g. SEOmoz - 362; note that this requires an additional term in the query to return results)
Gigablast Pages Indexed - via Gigablast Advanced Search
(e.g. SEOmoz - 1 page)
Exalead Pages Indexed - via Exalead
(e.g. SEOmoz - 5,481 pages)
Clusty Pages Indexed - via Clusty Advanced Search
(e.g. SEOmoz - 5,867 pages)
How this Site Looked in the Past - via Wayback Machine
(e.g. SEOmoz - all the way back from February of 2005)

Link Data

Yahoo! Link Data - via Yahoo! Site Explorer
(e.g. SEOmoz - 187,234 external links)
Technorati Link Data - via Technorati
(e.g. SEOmoz - 8,961 links from 2,541 blogs)
MSN Link Data - via Live.com
(e.g. SEOmoz - 107,512 external links)
Google Link Data - via Google (note that this information is purposefully inaccurate)
(e.g. SEOmoz - a uselessly erroneous 2,370 links)
Google PageRank - via RankAlert (shows for all 72 datacenters)
(e.g. SEOmoz - PR 5/10 or 6/10 depending on DC)
Exalead Links - via Exalead
(e.g. SEOmoz - 4,308 external links)

Social Tagging Data

Bookmarks at Del.icio.us - via Del.icio.us
(e.g. SEOmoz - 31 pages, thousands of bookmarks)
Pages in StumbleUpon - via StumbleUpon Reviews
(e.g. SEOmoz)
Mentions at Digg - via Digg Search
(e.g. SEOmoz - 50+)
Mentions at Reddit - via Reddit Search
(e.g. SEOmoz - 21)
Mentions at Tailrank - via Tailrank Search
(e.g. SEOmoz -
Mentions at Newsvine - via Newsvine
(e.g. SEOmoz - 1)

Third-Party Trust Metrics

Important Directory & Site Listings

Listings in the Open Directory Project - via DMOZ
(e.g. SEOmoz - 3)
Listings in Wikipedia - via Wikipedia Search
(e.g. SEOmoz - 12)
Listings in the Yahoo! Directory - via dir.yahoo.com
(e.g. SEOmoz - 1)
Listings in MSN’s bCentral - via bCentral
Listings in Business.com - via Google Search (as Business.com has none of their own)
Links in Google Groups - via Groups.Google.com
(e.g. SEOmoz - 134)