Youtube -- Skip the entertainment aisle and YouTube is chock full of learning on tons of subjects. Watch tech talks from conferences, recorded lectures for entire courses, dev community meetings, and tutorials for pretty much anything out there. For example, I stay current with quite a few projects (Kubernetes for one) by following their community meetings on YouTube. I've also gone through more than my ad revenue's worth of courses for free.
Bonus YouTube protip: If you pay for Google Music, you can also download any YouTube video and watch it offline (YouTube Red feature), and even keep playing the audio in the background when you turn off the screen. This alone probably opens up 10-100x more educational content for (non-data-plan-wrecking) consumption during my commute. My wife does use Google Music, and occasionally I do too, but I'd pay $10/mo just for the YouTube download/background functionality.
Podcasts [2] -- More free educational content. (Can you tell I'm all about that learning?)
HN Comments -- Great discussion with some really smart people who may have another interesting angle on a problem and nearly always are polite and reasonable in their responses.
[1] https://ocw.mit.edu/index.htm (A lot of their full courses are also on the MIT YouTube channel as playlists)