I'm not sure if this will help you, but here's a list of the keyboard shortcuts for watching YouTube videos -- http://www.makeuseof.com/tag/comprehensive-guide-youtube-player-keyboard-shortcuts/
They work when viewing videos using the Firefox browser, and as far as I know, are not browser-specific, so they should work with Chrome. They should probably work with other Flash videos as well.
I've found that in order to activate the keyboard shortcuts, I have to use my mouse to pause the video. Then, when I press the tab key, it will advance to the various controls, and the other keys will work.