If you value your online privacy the chances are you use Adblock Plus, Ghostery (or one of its competitors), and the Keyboard Privacy Chrome extension. Here's another extension to install.
While there are several good extensions that block tracking scripts, the EFF thinks that the existing blockers don't go far enough. As they explained in the FAQ:
Although we like Disconnect, Adblock Plus, Ghostery and similar products (in fact Privacy Badger is based on the ABP code!), none of them are exactly what we were looking for. In our testing, all of them required some custom configuration to block non-consensual trackers. Several of these extensions have business models that we weren't entirely comfortable with.
The EFF doesn't offer specifics on what they block compared to other blockers, but they did say that the 1.0 release is focused on only blocking third-party trackers. For example, Privacy badger will not block Facebook from tracking you while you are on its site. (However, the extension does let you choose to block a site's trackers manually.)
They also noted in the press release that Privacy Badger 1.0 is designed to work with the new Do Not Track (DNT) policy that the EFF announced earlier this week. Users can set a DNT flag, and any tracking service that promises to respect that flag will not be blocked by Privacy Badger.
I don't know if that's true but I have been playing with Privacy Badger for a few minutes and it is much more security-conscious than Ghostery - possibly to the point of paranoia.
Privacy Badger identified a couple trackers on Twitter that Ghostery let through. I blocked the trackers and discovered that they weren't trackers but were instead core parts of the Twitter platform (blocking them broke Twitter).
Clearly, caution is in order.
Edit: Privacy badger is also marking the sharing buttons as trackers (a nice touch).
The EFF wants to release Privacy Badger for Opera, Safari, and Firefox Mobile, but IE is not on the list. Microsoft's legacy web browser "appears to be incompatible with how Privacy Badger works at a technical level".
image by Chris_Parfitt