There is also the option of downloading with http://rg3.github.io/youtube-dl/ and queuing up the local files in your preferred local media player's playlist support. Particularly useful if you might want to watch the content while travelling as you don't need a reliable connection as you would for streaming.

yt-dl directly supports a fair few other video sites (http://rg3.github.io/youtube-dl/supportedsites.html) too, and indirectly a large number of others as its generic resource locator does a fairly good job of finding the object you want unless the site actively tries to obfuscate the video's location.