How to Search People and Gather Information online ?

There are some cool website which will allow you to search People  and gather information about the people  , Organisation , Network ,DNS etc.  Most of which are used by Hacker and Penetration tester  for information gathering .
    Here are the some useful list for Information Gathering .There may be more out there but for me it's best .

http://www.pipl.com /

http://www.isearch.com/

http://www.centralops.net/

http://www.archive.org/

http://www.alexa.com/

http://www.domaintools.com/