Via Allan McRae I found out about YoutubeCenter, a userscript and/or add-on for Firefox and Chrome.

youtubecenter

This script come with many handy features that make the Youtube experience way nicer!

Some really nice features I used are:

  • Remove ads
  • Resize the player
  • Buffer the video even when paused
  • Provides download-links
  • disables auto play
  • thumbnail animations
  • and many more!

Go get it here!