Lifehacker has a rundown of recommendations for simple browser add-ons (such as Disconnect, Do Not Track Me, and the adorably-mascotted Ghostery) for keeping your online browsing and communications safe from tracking:
Anti-tracking and anti-cookie extensions have exploded recently. Disconnect (Firefox/Chrome/IE/Safari) is our pick because it continues to add useful features and improve its database, and its secure Wi-Fi and bandwidth optimization features aren’t available in other tools. It blocks third party tracking cookies and gives you control over all site scripts and elements from a simple-to-use toolbar menu. It also protects you from tracking by social networks like Facebook, Google, and Twitter, which use your browsing even off-site to collect data about you.
HTTPS Everywhere (Firefox/Chrome) is a must-have regardless of what other security tools you opt to use. Once installed, the extension will shunt your connection to SSL whenever possible, and will try to find secure versions of the sites you visit.