Podcasts are new—okay podcasts were new about 10 years ago—but the reference format will look familiar. As with other retrievable documents, just follow the basic guidelines for creating a reference: Tell the reader who, when, what, and where. When in doubt, this post on citing something you found on a website always helps me!
For a podcast, the “who” might be a producer, a writer, or a speaker. You can use parentheses to identify the contribution of the person in the "who" position—when you know it.
For example, here’s a reference for an audio podcast:
|Rissian, L. C. (Producer). (2012, May 4). Twelve parsecs [Audio podcast].
Retrieved from http://itunes.apple.com
Notice that the “Retrieved from” line includes the homepage URL, not the full URL, of where you found the podcast. (In this example, it was an iTunes page, but it could be an organization's webpage or even a website devoted solely to the podcast.) A full URL might feel more direct, but the homepage URL is more likely to be correct as the days, months, and years pass between when you create your reference and when a reader sees your work and wants to find the podcast.
Video podcasts are also new—okay video podcasts were also new about 5 years ago—but you can cite them in the same fashion. In an earlier post, you’ll find an excellent sample reference to a video podcast.