Some extensions that you could try:
Stop third parties and search engines from tracking the webpages you go to and searches you do.
- Disable tracking by third parties like Digg, Facebook, Google, Twitter, and Yahoo, without requiring any setup or significantly degrading the usability of the web.
- Truly depersonalize searches on search engines like Google and Yahoo (by blocking identifying cookies not just changing the appearance of results pages), while staying logged into other services — e.g., so you can search anonymously on Google and access iGoogle at once.
- See how many resource and cookie requests are blocked, in real time.
- Easily unblock services, by clicking the toolbar button then services (and reloading current pages) — e.g., so you can play games on Facebook.
Stop worrying about ever-changing privacy policies and take the first step towards getting control back over your information.
DNT+ keeps an eye out for advertising companies and social networks looking to gather your personal information.
- Free tool that puts you back in control of your information
- Best available blocking stops more than 600 trackers
- Compatible with Mac or PC for Chrome, Firefox, Safari, and Internet Explorer
- Automatically updates to catch new trackers
Sets permanent opt-out cookies to stop behavioral advertising for 100+ different advertising networks, including Google, Yahoo, Microsoft, all members of the Network Advertising Initiative, and many other companies.
Blocks 3rd party Tracking, Statistic Collecting and other code which breach your privacy. It is Recommended to use this list if you do not want your personal information to be collected by websites and Ad Companies.
EasyPrivacy is an optional supplementary subscription that completely removes all forms of tracking from the internet, including web bugs, tracking scripts and information collectors, thereby protecting your personal data.
This extension may also be of interest:
Discover who’s tracking you online
Collusion is an experimental add-on for Firefox and allows you to see all the third parties that are tracking your movements across the Web. It will show, in real time, how that data creates a spider-web of interaction between companies and other trackers.
Note that except for Beef Taco, all Firefox extensions listed here are also available for Chrome. An equivalent of Beef Taco for Chrome is Keep MORE Opt Outs. Collusion for Chrome (made by the same people who made Disconnect) can be downloaded here.