The new help system in Mac OS X Leopard is fantastic. Not only is it unified and standardized across all applications, but there is a hidden gem inside of it, that is, it can help you find those hidden menu items in your application quickly!
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!