In a search for informative, engaging educational podcasts, I came across "A History of the World in 100 Objects" by The British Museum and the BBC. http://www.bbc.co.uk/ahistoryoftheworld/about/british-museum-objects/
Each episode focuses on an object at the British Museum, starting with an Egyptian sarcophagus from 254 BC, and working through time to a Chinese solar powered lamp, made in 2010 AD. It's a nice way to look at history through man-made artifacts and art, as opposed to the history of events and conquests. That type of historic overview is especially useful in the art curriculum. Although the content is too erudite for the elementary students, it's a good resource for the teacher.
The segments are short; less than 15 minutes each. And the website includes photographs of each object, as well as a transcript of the podcast for those who prefer to read. You can also read comments from other subscribers on the website, although the comments don't appear to be moderated.
The series is a few years old, and is not adding new episodes. But since 98% of the content is ancient history, that should not be a factor for most listeners