These very informative podcasts have broadened my horizon and helped me through the long and boring traffic (and sometimes boring days at work) 
You can either download them manually or subscribe to them on iTunes or zune and it will download new podcasts regularly.
Have a great listen!
The naked scientists (60min.) : Weekly show, discusses various scientific and technological topics, and has a weekly “kitchen science” segment which you could try at home.
http://www.thenakedscientists.com/
Tech Weekly (30min.) : Discusses contemporary science topics.
http://www.guardian.co.uk/technology/series/techweekly
Material Matters (30min.)
http://www.bbc.co.uk/radio/podcasts/material/
Science in Action (30min.)
http://www.bbc.co.uk/radio/podcasts/scia/
Science with Dr. Karl (60min.): Dr. Karl answers all sorts of itchy science questions from all over the world
http://www.bbc.co.uk/radio/podcasts/drkarl/
