A lot of browser addons or extensions claim to improve privacy and security. These include Ghostery, Disconnect and Privacy Badger along with a slew of others.
I think for most entry level computer users that those type of addons might provide something useful. To people who are more experienced with browsers and their extensions they seem like a gimmick or just fancy visual feedback. A lot bells and whistles with very little actual functionality.
What can really make surfing the internet a much safer experience? If we focus on HTTPS, SSL and Digital Certificates then we have a good head start. From there we can protect ourselves from ads that might lead to sketchy websites. We can beef up our passwords and add authenticators to our accounts. At the most zealous level we can disable javascript and flash.
The following extensions are for Chrome.
https://chrome.google.com/webstore/detail/adblocker-ultimate/ohahllgiabjaoigichmmfljhkcfikeof?hl=en
Adblocker Ultimate accomplishes the two jobs that all adblockers must. First it has to have a pretty good idea of what is undesirable content and what it is that users want to see or interact with. Also there are no false positives; Adblocker Ultimate pretty much never identifies images or other website content as ads when they aren't.
The extension is also easy to turn off. You can disable it entirely or just for a webpage. The function that allows you to add new blocked elements works extremely well.
https://chrome.google.com/webstore/detail/authy-chrome-extension/fhgenkpocbhhddlgkjnfghpjanffonno?hl=en
Authy integrates authentication into the browser. I have not personally used this extension. The use of authenticators is extremely powerful security wise. I prefer to use my phone and download apps that have authenticators because I see having two different pieces of hardware as more secure than an application running beside another on the same device.