It is rather simple to create Podcasts. You simply record a conversation. That conversation could be in person, over the phone, or in many cases over Skype.
Where it becomes difficult is processing the recording. As anyone who has tried to post a podcast in its raw state, it can be very difficult to follow due to the varying volumes of voices. There are 2 tools out there that can help with this process.
One of of the most popular open source products is Audacity. This is a complete recording studio for Windows, Mac or Linux. It is available for download here.
A new product is out in Beta called the Levelator from Gigavox Media. It is simpler, yet more complex. Audacity will level the volumes, but does it in real time as it is playing the track. Levelator creates a map of the full track first, then applies some algorithmsÂ to level the volumes.