People have also recommended using the following for in-depth scholarly searches
 http://huskysearch.cs.washington.edu/
 http://www.alltheweb.com
 http://www.allthesites.com
 http://www.northernlight.com

while for finding plagiarism these have been commended:
http://www.findsame.com
http://www.coastal.edu/library/papermil.htm
http://www.plagiarism.com (a commercial site)

There is also a site that regularly copies and archives millions of URLs as they develop and disappear. It allows one to view sites that are no longer available, as well as earlier versions of still available sites.