The Electronic Freedom Foundation (EFF) has created a browser extension for the Firefox and Chrome browsers that automatically detects and blocks spy ads. According to the EFF, Privacy Badger "analyzes sites to detect and disallow content that tracks you in an objectionable, non-consensual manner." If a website attempts to track you without permission, or attempts to install tracking images, scripts, or other information on your system, Privacy Badger will automatically disallow the content.
Cookie-blocking settings and features have been around for years, but tracking techniques have become much more sophisticated. Trackers now have spying techniques that go well beyond what you can catch by merely blocking cookies. Privacy Badger can stop the cookies, but it also detects and stops other, more sophisticated ploys.
Interestingly, the EFF says Privacy Badger will unlock advertisers and other third-party domains that make a strong commitment to support the Do Not Track option. Do Not Track (DNT) is an optional browser setting that notifies the website that the user does not want to be tracked. The DNT concept only works if websites respect it. The EFF asks that vendors post the Do Not Track Compliance policy and commit to respecting DNT in order for the site to be unblocked.    
Privacy Badger is still at the alpha release stage, and the EFF is actively seeking feedback from testers.