Not sure if this is a thread already, couldn't be arsed searching. So, I'll start with a few of my regular listens:
Full Disclosure with James O'Brien
RHLSTP (Richard Herrings Leicester Square Theatre Podcast)
Mysterious Universe
I've Been Thinking with Peter Frankopan
WTF with Marc Moran
The Adam Buxton Podcast
Radiolab Podcast
Search for them in your favourite podcast app should you wish. I'd be interested in hearing what tickles your conversal fancy.