vdNote - Share noteworthy moments from YouTube videos.
you-tldr - Get the tldr of any YouTube video in seconds
YouDict - YouTube dictionary to search words, expressions & names
SliceTube - The Fast and Modern way to cut and download YouTube videos
Summary Panda - Remove annoying 'blah blah blah' parts of YouTube videos.
GIFit! - Quickly turn YouTube videos into GIFs (chrome extension)