The Washington Post has a list of some things you can do to increase your security and make it harder for the government to keep tabs on you.
If recentreports are to be believed, the National Security Agency has broad powers to capture private information about Americans. They know who we’re calling, they have access to our Gmail messages and AOL Instant Messenger chats, and it’s a safe bet that they have other interception capabilities that haven’t been publicly disclosed. Indeed, most mainstream communications technologies are vulnerable to government eavesdropping.
Here is an explanation of TOR, software that allows anonymous browsing on the internet: