No surprise, Google currently holds the #1 spot. We remember when Yahoo was king and Google had yet to be born. In the early days there were a dozen or more search engines considered to be major players. Today, Google, Yahoo and MSN collectively dominate over 95% of all search engine traffic (keep in mind that AOL pulls their results from Google as well). Thus, when it comes to search engine optimization and search engine marketing services, our main focus is generating top positions within the big three - Google, Yahoo & MSN.
Google also supplies results to Earthlink, AT&T and dozens of other partners. Yahoo has since purchased Overture, AltaVista, FAST and Inktomi, making them Google's #1 competitor.
(Other smaller search engines include Ask, Dogpile, Excite, Netscape, MetaCrawler, Search.com, AllTheWeb, Lycos and HotBot)