The most popular search engines are Google, Yahoo, Bing, Ask.com and AOL.com. Wolframalpha, DuckDuckGo, WayBackMachine and ChaCha.com also provide popular search options. Out of them all, Google is the most popular by a wide margin, as of 2015.
Google, the most popular search engine in the world, gets around 1.1 billion unique visitors per month. Google searches are the most popular for both computers and mobile devices. Microsoft's search engine, Bing, is the second most popular search engine in the United States with 350 million unique visitors per month.
Ask.com, which used to be AskJeeves.com, is a question and answer based search website that has questions answered by mostly either other users or by the use of polls. The website does also have a general search ability similar to Google and Bing, and it receives about 245 million unique visitors per month.
Wolframalpha is different than other search engines in that it utilizes what they call a Computational Knowledge Engine to gather results. It is particularly good at performing calculations and pulling up facts.
DuckDuckGo is unique among search engines because it does not track its users and is not packed with ads.
An Internet archive, WayBackMachine can pull up a website going back to 1996.