I listen to a lot of history podcasts, and though they vary a good deal in quality, the ones by experts in the field (people with a PhD in History focusing on the subject) like The Fall of Rome podcast, the Ottoman History podcast, or the Religions of the Ancient Mediterranean podcast are an excellent source of information. If you look for them, though, keep in mind that a lot of history podcasts have similar names. For example, the aforementioned Ottoman History podcast is different from The History of the Ottoman Empire podcast.

The one by amateurs vary a lot in quality. Some - like the History of England podcast - seem to be done by amateurs who are extremely well informed (though skip the first 20 episodes of the History of England podcast if you give it a go). Others seem to be about the same quality as someone giving to you a synopsis of a Wikipedia page they just read. When in doubt I'd stick to the ones by experts in the field.