iTunes 11 features a new MiniPlayer that has enough advanced functionality to allow you to control playback without the main iTunes window. You can also bring up a movie window that doubles as an artwork viewer. You can set both to remain on top of all other windows and apps allowing you to control your music playback while doing other things with your Mac.
With "My Queue" you can quickly save videos to watch later.
To add an item to your queue just click the sign next to the video.
Once you've added a video visit "My Queue" to start watching!