When watching a tutorial on YouTube, click on Settings (the gear symbol in the play bar) then choose “speed” and then choose "1.5".
You’ll be watching the video in only 2/3 of its time while still being able to understand the instructions.
With this method, a tutorial of 10 minutes can be watched in 6 minutes and 40 seconds.
It's pretty useful when the person speaking is slow or when there's not much talking in the video.
You can also use this trick with your keyboard:
For Chromium users under Ubuntu do Shift + ? and Shift + .
Enjoy!