If you want to browse the internet anonymously, and you are patient enough to wait about 2-3 seconds for web pages to load, check out Tor.
Tor is a network that protects you by bouncing your communications around a distributed network of relays run by volunteers all around the world. Tor prevents somebody watching your Internet connection from learning what sites you visit, and it prevents the sites you visit from learning your physical location. Tor works with many of your existing applications, including web browsers, instant messaging clients and many others.
There are an estimated 500,000 users of Tor. These include law enforcement and intelligence agencies in the United States, which was the intention of the US Naval Research Lab when it invented the underlying technology and funded the early development of the project. Tor is also used by activists, journalists and the general public in Iran, Syria, China and other countries with authoritarian governments, which has led to significant funding for Tor from the US State Department and the Broadcasting Board of Governors. However, Tor is also used by many people in the United States—it is estimated that approximately 15% of the users of Tor are located in the United States.