If you're not already receiving Melvyn Bragg's weekly musings email, stop whatever you're doing and go and sign up. It's lovely.
You can also sign up for In Our Time directly at the iTunes Store (along with From Our Own Correspondent and a host of other stuff from BBC Radio.)
In our time is the most interesting and challenging programmes put out by the BBC. Sometime the subject is a sceintific one. I find it beyond my comprehension but I still listen for the sheer pleasure of hearing great minds at work. Long may it continue.