TheSearchEngineList.com provides a comprehensive list of free search engines that it sorts by category. About.com provides a short but current list of the best free search engines of 2015.
Some search engines specialize in specific subjects or content. For example, FreeBookSearch.net searches digital libraries around the world for free online books. CheatSearch.org searches for cheat codes for games. Monster.com is a large job search and resume database search engine.
As of 2015, the most popular search engine is Google.com with over 11 billion searches per month. Google.com is a general use search engine that provides search results from all around the Web.