AnswerThePublic.com: that free visual keyword research & content ideas tool
from Diigo
Top 1 Million Websites and the Top Level Domains used to Build Them | Research gTLDs, ccTLDs and IDN
Software: Business & Nonprofit | Reviews and Top Software at Capterra
The Free Keyword Tool from WordStream - Free Keywords for SEO, AdWords, & Blogging
Pipl - People Search
splunk'd
Nielsen NetRatings Search Engine Ratings
Pew Internet & American Life Project Report: Search engine use
ResearchBuzz
ResourceShelf