You can still do it, though it's a little harder: click the gear icon at the bottom right of the video, select speed, choose your speed.

The gear icon is no longer available (at least in Chrome). Interestingly, I just tried Firefox and Edge, and both still had the gear icon available. I guess I will be watching in one of these browsers from now on.

I had to switch computers 6 months ago (my chromebook died) and in going over to a windows machine began using the edge browser.  But it seems that I've lost the ability to change the speed on videos after the switch. No "gear" icon. I advise students having trouble in the grammar curriculum to set the speed for half when they don't understand. My advice is no longer good.  today I wrote to someone that she would have to watch the videos outside of Khan Academy, getting them directly on YouTube for this to help her.  I regret having to advise going outside.  PLEASE bring back the settings icon!

Please bring back speed controls. Watching videos at regular speed is torture. I watch many YouTube videos on 2x speed or faster if the person is talking slowly or taking long pauses.

Having speed controls and quality controls are non-optional in my opinion.  Quality is required to read handwriting on the screen.  Speed controls are required for some students to understand what is said (time compression, 2x, etc.).  Please prioritize getting them back for the browsers that are affected (Chrome, etc.)

This may be useful to some people ...

At some point in the past, I inexplicably lost the ability to change the playback speed (ie, the gear icon, etc), and then, after a few weeks, it returned again. Then, today, I lost the ability to change the playback speed again. I noticed at the bottom of the video window a link to "show full player" (or something similar to that), and when I clicked on it, the full video controls were restored (with the ability to change the playback speed). 

Some people may also find this link helpful:

Is there a way to speed up Khan Academy videos by 1.2X, 1.5X, or 2X? - Quora

https://www.quora.com/Is-there-a-way-to-speed-up-Khan-Academy-videos-by-1-2X-1-5X-or-2X

any update?
Currently on Chrome there is not option to change the speed.

I have chrome and am able to speed them up through the gear button. 

It is possible to me to change speed, but it is painful have to do it for each single video
i think would be better if had a "global option" for playback speed, or it save the speed i've put a video, and pla the next one in the same speed

If your settings/gear button disappears, do this:  Click on "Go to lesson page," then look at the bottom right, just below the video, and click on "Switch to full player."  Problem solved.  ;-)

Yes please that is such an important feature, please bring it back

There is still a way to do that (when there isn't a gear icon on the bottom of the video player), by using firefox, you can right click a video several times *consecutively* you will see the native html5 video options appear in the context menu then select the playback speed control to adjust the speed.