We were pretty active on the 'Top television' thread a while ago. Now we can be active on the 'Top radio' thread - radio-active, if you like.
One of the best things on Radio 4 is Jim Al-Khalili's series, The Life Scientific, though I rarely remember in time to listen.
The iPlayer list of episodes is here. Recent topics include Jodrell Bank's Tim O'Brien on transient stars as well as science and music festivals; a new theory of space-time; how time and space began; Saturn; Neil de Grasse Tyson on Pluto (no, not on Pluto - talking about Pluto); Roger Penrose on black holes; Sheila Rowan on gravity waves; dark energy; an interview with Britain's first astronaut; Helen Sharman; dark matter; Matt Taylor on the Rosetta mission - tonnes of stuff, as well as plenty of episodes on mathematics, biology, geology, engineering and other subjects that Sheldon Cooper wouldn't approve of.
Enjoy!
"Observatories are cathedrals of science." - Tim O'Brien