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