Do I Need a Microphone?
Apart from your content, a good quality USB microphone that plugs into your computer is an absolute necessity, particularly if you are hoping to submit your podcast to iTunes.
People just won't want to listen if the sound is muffled and so this is one investment that you will never regret. Be sure to do your research (condenser vs dynamic) and shop around.
Condenser and Dynamic Microphones
In general, dynamic microphones are what you will find in professional recording studios, while condenser mics are the preferred choice of many creating home podcasts, particularly if there are several presenters.
A dynamic microphone is more directional, meaning that if you turn away, this will be noticeable in your voice, which will fade slightly. However, the advantage with this option is that background noise will be kept to an absolute minimum.
Condenser microphones tend to be more affordable, creating a really rich and crisp sound. They will be able to record your voice or voices regardless of where you are facing. If you look towards someone and turn your head, it won't really be noticeable. What this does mean, though, is that background noise may well become problematic, so it will be absolutely essential that you choose the quietest room possible, without any interruptions.
When you are ready to make your podcast, test your microphone by doing a quick recording to check the sound levels. It is much easier to make adjustments before your recording, than afterwards, so don't rush this important stage.
Amazon and eBay are good starting points for your quest, be it for a Blue Yeti, CAD Audio or an MXL990 microphone, although most are incredibly sensitive and will pick up all kinds of background noise, so it is worth stressing again that peace and quiet when you are recording is essential.
A pop filter shield may be worth adding to your shopping list, particularly as they are so inexpensive, although you can actually have a go at making these yourself.