Our regular Uncanny podcasts happen monthly, and feature one story, one poem, and an exclusive interview. There are two podcasts per issue (because we only do 6 ebook issues a year).
You can check out previous podcasts here: http://uncannymagazine.com/type/podcasts/
They are also available on iTunes and through other podcast management programs/apps.
The Special Exclusive Podcast for backers is a one-off episode recorded separately, often on a random (but hopefully entertaining) topic and is exclusive to backers--we only share it via dropbox with our backers at the levels that get access to it. It doesn't get released as part of our general podcast.