Search has been consolidated to a few major players. In some regional markets, there might be important local players, but for most of the world, Google, Yahoo!, and MSN control the bulk of search.
The Major Search Engines

The following search engines are reviewed in order of search distribution from the best of my knowledge. Some of the first-listed search engines may appear to have more content and more information than the later-listed search engines. There are several reasons that the top couple search engines have much more data listed in their sections:
Much of the data from one section would carry over to the next section.

Companies that have been focused on search the longest are more likely to have plugged algorithmic holes.
Google is MUCH harder for new webmasters to manipulate than the other engines.

The order of these listings has nothing to do with the relevancy or quality of the search results. They all provide quality results using somewhat similar algorithms.

Section Modules

• History of the Web & Search. Background article on the history of search.
• Search Engine Submission. How to get listed in search engines. Also includes information about paid inclusion.
• Google. The leading search engine.
• Yahoo!. The second most popular US search site, powered by Microsoft Bing & Microsoft adCenter.
• Microsoft Bing. Google’s top rival.
• Ask.com. Smaller search player which is bowing out of search. And there are also a few new smaller search engines like Blekko and DuckDuckGo. Some Asian markets are dominated by local players: Baidu in China, Yandex in Russia, and Naver in South Korea.
• Comparing Search Results. An explanation of why search engines have different search results.
• Local Search. how to optimize local oriented websites for search. Also contains tips for multilingual websites.
• Vertical Search Engines. Other search engines, and niche databases that get pulled into global search engines.