"Viewable with Tor
https://www.torproject.org/index.html.en
installed, search engine DuckDuckGo
http://duckduckgo.com/
 has erected a hidden service for secure, encrypted searches through the Tor network.
http://en.wikipedia.org/wiki/Tor_(anonymity_network)
 While past attempts at hidden service search engines
http://www.weblens.org/invisible.html
 failed due to uptime or quality issues, DuckDuckGo marks the first time a real company operating a public search engine has offered a solid search engine as a hidden service for Tor users.http://www.gabrielweinberg.com/blog/2010/08/duckduckgo-now-operates-a-tor-exit-enclave.html"
http://www.lib.berkeley.edu/TeachingLib/Guides/Internet/InvisibleWeb.html