These are my current favorites:
Serial is a spinoff of This American Life (another one of my favorites). It explores the true story of a murder committed in Baltimore in 1999 over an entire season of episodes. I am 100% sucked in and it's painful to wait an entire week for each new episode. I just want to know who did it already, dammit!
I recently discovered Stuff You Missed in History Class and have been loving it. I am a total history nerd, so this is right up my alley. I will admit, some of the topics can be a bit... dry. So I just scroll though the list and look for topics that I might find interesting.
The Savage Lovecast is awesome. It is hosted by Dan Savage, a relationship and sex advice columnist. If you are easily offended by... well.. anything, then this is not the podcast for you. My sex and kink knowledge base has expanded significantly since I began listening to his podcast. Now I can't help but wonder what kind of weird shit people I know are into because ohmygod... I can't even... you just have to listen. Your mind will be blown, TRUST ME.
Radiolab has been a favorite of mine for years. It is just two dudes exploring topics and concepts that they find interesting. I don't know what else to say. Just give it a listen, you won't be disappointed.
Do you have a favorite podcast? I would love some recommendations!