Search Engines: 

alltheweb -- alltheweb visits over 2 BILLION web pages, and offers an offensive content filter for English language documents.
  

Alta Vista  -- Alta Vista offers an advanced search feature, and an optional family friendly filter for safer searching options.

Ask Jeeves or Ask Jeeves for Kids -- both search engines use natural language features, you simply ask the question and await results.  Ask Jeeves for Kids is a tool for elementary students.

Google   -- currently one of the best search engines available.  Google searches over 3 BILLION web pages to return results. Google will search for images as well as documents.

Mamma  -- is a meta-search engine.  Meta-search engines will search several search engines for results.  Mamma will eliminate duplicate results and can handle complex searches.  Mamma also has a domain filter, which will restrict to or exclude a particular domain type.  (You can limit your searches to .edu sites, for example.)