Fraidycat is a desktop app or browser extension for Firefox or Chrome. I use it to follow people (hundreds) on whatever platform they choose - Twitter, a blog, YouTube, even on a public TiddlyWiki.

Browser extension to copy hyperlinks, images, and selected text as Markdown

Contextual unit and timezone conversion on any web page (units: several metric/Imperial, both ways, configurable; timezones: any timezone to your local time).

To pronounce a English word, do one of the following:

a free, easy-to-use Firefox extension to help you collect, manage, and cite your research sources. It lives right where you do your work — in the web browser itself.

stop button should disappear when it is disabeled, the same thing for t reload

Arabic version of Rediscover the web.