I watch a lot of lengthy YouTube videos, mostly instructional-type videos from Google Developer Advocates and the like, explaining how to use APIs, tools, etc. They're good, but every time I look at one and see that it's 45 minutes, or 70 minutes, or whatever, I kind of cringe and sigh. Sometimes I just put it on a "to watch later" list, and maybe I don't get around to it for a long time, if ever. Recently I discovered a useful way to shave a good chunk of time off that watching experience. It's been around for a while, but I wasn't aware of it. YouTube has a trial version of an HTML5 video player that allows you to set the playback speed to 1.5x or 2x normal speed. I find 1.5x to be useful; 2x seems to be too fast if you want to understand the audio, but it could be useful for fast-forwarding to the next interesting part.
For details on enabling this feature, checkout the write-up here.