This add-on injects CSS and Javascript to remove feed and notifications in Facebook, Twitter and Linkedin. You can choose to active or not this behavior directly on the page (next to the URL).
The addon is available here addons.mozilla.org/addon/stay-productive
The extension is available here chrome.google.com/webstore/detail/stay-productive
The addon is available here addons.opera.com/en/extensions/details/stay-productive/
No submission in respective stores so far, but you can already add this add-on by using the chrome branch of this repository and add it in the developer mode.
This add-on use the new technology WebExtensions, in order to have compatibility with other browsers. Install web-ext to test and build releases.
If you want to improve something make a pull request and if you have a bug open an issue.
Inspired by kill-fb-feed