[poopers]

These are the ones I listen to the most. All are on iTunes, but I've put direct links to the sites in too:

Radio Le Mans (specifically their "midweek motorsport" podcast)
http://rlm08.0157.org/

TWiT (This Week in Tech) - a light-hearted look at tech news.
http://twit.tv/twit

No Agenda - well researched conspiracy theories (not crackpot alien stuff), very funny too.
http://www.noagendashow.com/