One I quite like is a guy called Ben Greenfield at www.bengreenfield.com
He's a serious competitve triathlete (some sort of American champion - perhaps in his age group) and talks about a whole range of stuff: running, nutrition, gym routines, lifestyle, you name it. Yep, there is the usual U.S. slickness but it's not exessive and the guy is genuinely knowledgeable. He has a particular take on nutrition which is always interesting even if I don't agree with all of it.
Worth a listen though. Length is usally around an hour to 90 minutes so good for a gym session.