According to the Wordtracker record. Google is the most popular Search Engine by all internet users.

68.74% of all internet searches are performed by Google today. Yahoo is next at 19.08% and MSN is third at 7.63%.

            

There are other search engines, such as Ask, Altavista and Alltheweb, that are insignificant, so don’t even worry about these when doing search engine optimazation to your websites.