Bing - Microsoft’s search engine which includes news, free Email and other features.
Google - The world’s most popular search engine, which includes special tools such as Google full text search, Google Scholar search for academic articles and papers, Google Earth geographic search and free Email. Includes language translation tool.
Yahoo! - A popular search engine. that includes directory and specialized searches, news, financial information, Email and much more.
About.com - Guidance from real people searching the Internet for the information, goods and services that you need to know related to your passion.