What are good podcasts for free?
Technically speaking, they all are. The short answer is to start with an internet search for "good free podcasts about..." and you'll find a few. But, good podcasts are relative to each listener. What makes a podcast good? Generally, the intro; the host; the contributors; and the conversation. Sometimes though, even the topic by itself can make a podcast good. Depending on your niche, mood, preference, or social circle, any podcast could be good in that moment. The best conversations though require the host, guest, and audience to be present in the moment, and actively listen, in order to become "good," "better," or "worth listener's time." Moments aside though, what makes podcasts good is that they aren't FCC-regulated. The Federal Communications Commission exists to regulate radio and television communications, to promote competition within broadband services, and "...to provide leadership in strengthening the defense of the nation's communications infrastructure..." to list a few things.
What the Presidentially-appointed directors and the FCC are also responsible for though, is "...encouraging the highest and best use of the radio wave spectrum domestically and internationally." Oddly enough, that doesn't include podcasting. Podcast journalism, whether for entertainment or education, is far and away becoming one of the best uses of radio waves streaming over the internet. It's like crowdsourcing the sum total of our human existence into a creative outlet that in some form or fashion appeals to everyone. Edison Research and a few other research companies are focusing on podcasts and their impacts on society. Sicne its Golden Age, radio has had ebbs and flows of popularity but never prohibition or degradation. People need to watch all sorts of important things one at a time, but can still enjoy audio learning in the background of their busy lives. While there are some podcasts that charge money for premium content, most podcasts are free; and depending on your mood, all of them are good. Any time people co-exist and share their humanity or experiences for the betterment of others, it historically has always ended well. However, you determine or qualify your "good" podcasts, survival takes communication.