Google

Google is the largest and most popular search engine on earth. Google's market capitalization is $197 billion as of February 2011. They offer a wide range of internet services, many for free, including:

• Search Engine for all types of internet media
• Office Productivity software
• Email
• Translation Service

They have acquired many companies which has given them access to a large portion of internet traffic, including:

• Urchin, now Google Analytics
• Blogger
• DoubleClick
• YouTube
• FeedBurner
• ReCAPTCHA

Google makes the majority of its revenues from its advertising programs, specifically:

• Google Adwords
• DoubleClick

Read more about Google on Wikipedia