I have been watching a fast-moving video that I'd really love to dissect in slow motion (half or quarter speed; frame-by-frame isn't necessary in this case). Is there a quick and easy way to accomplish this?
I don't think it is possible unless you download the entire video on your machine. YouTube's Flash Player does not have such an option.
You can also use www.pausehouse.com. It's a really cool website, that lets you change the slow motion speed of YouTube videos, repeat selection, and even flip the image. Thus you can learn moves from YouTube videos with ease.
www.watchframebyframe.com supports half and quarter speed (frame-by-frame and precision timing as well!).
You don't really need to much. Just download the Chrome extension from EmbedPlus. You can learn more here: