There are two types of search engines 1. Hybrid search engines 2. Meta search engines
this site shows you the answer. http://searchenginewatch.com/2156451
Google & Yahoo are two main search engines.
Google, Yahoo, Bing are biggest search engines. There are some more search engines like Astalavista, Lycos, Ask, etc.
search engines and directories
Two words, search engines. Most NPOs have a website and would be connected to google's search engine. You could of course use other search engines like bing, yahoo or even altavista.
Meta engines search for information on different search pages at the same time. If someone typed in "hummingbirds" they would search on two or three search pages at once.
search engines
Search engines have two major functions: crawling and building an index, and providing search users with a ranked list of the websites they've determined are the most relevant. Thanks, Ekavat
Bing (www.bing.com) Google (www.google.com)
Alta Vista and Lycos. Yahoo and HotBot
www.askkids.com and www.kidsclick.org are pretty good.