The podcasting industry is a very fluid space so the term "network" is very loosely applied in terms of this list. What you'll find below is a mix that includes established media companies that have gotten into podcasting, independent studios that produce their own shows, and companies that have bought other companies that create content. This list is not meant to be comprehensive but is a good indication of the breadth of activity in podcasting at the moment.
For a more dynamic view of the podcasting space, you can consult:
Who Owns Who in Podcasting
