Podcasting can take many formats, just like a television show or radio program. In fact, since podcasting is so new and people are willing to experiment with different kinds of formats, you are likely to get away with formats that will not be considered acceptable in a television or radio program.
The interview show. In each podcast you interview one or several experts in the niche you serve.
The call in show. In this format, people phone in and you talk to them. This works well in any problem diagnosis situation, where people ask you for help with their garden or their car or their computer and you give advice to them but it is practical enough advice that all of your listeners will find value in it.
The monologue. In this format, you simply tell people your ideas, just as if you were a professor in a college lecturing your students or a storyteller with a rapt audience. If you have something interesting to say and you are a good speaker, this format can work well, especially since podcasting is the only medium that will allow you to do this. But be careful! Because it can become boring very, very quickly.
The dialogue. This format is much more enjoyable to listen to, even though you can accomplish the same thing in this format as you can in the monologue; get your ideas across to your listeners. The only difference is, two or more people are talking about it and the different invoices will help break up the format, and may even allow for a question-and-answer style discussion or a debate with one person on one side of the issue and the other person on the other side of the issue.
The conversation. This is a little less formal than the dialogue (above) and a lot more freeform. There are some great podcasts out there of just conversation-style shows, but they are difficult to maintain quality content without a script.
Podcast version of seminar/convention. This format is somewhat difficult to listen to, although if your industry has a convention that you cannot make it to, this is the next best thing. When the speaker of the seminar speaks into the microphone, it is also transferred into an MP3 format and then made available for you to download. If the seminar requires a lot of visuals, the podcast can be very boring, but it's the best option if you can't make it.
This quiz show. This is an interesting format, and it can be done in a couple ways: some podcasts ask questions, pause for some music while you think of the answer, then reveal the answer.
News magazine format. News channels, like CNN, are putting their headlines into podcast form. Like a television or radio broadcast, they simply list off the headlines then have a feature story or two followed by a few smaller stories. It's a good way to catch the news if you're on the go and want quality news from a respected national news source rather than local news from your radio station.
Of course, there are many other formats, but these are often the most popular. If you're creating a podcast you'll probably want to use these formats in a combination to provide the very best value to your list.