I've started watching TV Shows at 2X speed. This has been incredible:
I started doing this a few months ago. It started when I realized that I already listened to Audiobooks at 2X-3X, and that TV Shows are basically the same thing.
Some tips:
I've switched from VLC to Daum's PotPlayer which has fantastic support for youtube videos and playlists and allows speeding up videos like this. It also uses significantly less memory and cpu than watching youtube in firefox.
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.