This is something that is fairly easy to learn and also in high demand. On Windows, one good program to edit audio is Sony Sound Forge. I use Sound Forge Audio Studio, but if you are doing this professionally, you might consider the upgrade to Sound Forge 9. Get the hang of editing out um s and ah s from audio. Even better is understanding the flow of an interview conversation and editing out portions that don't make sense. Finally, learning to find and add intro music really gives podcasts that professional touch. Advertise your services on oDesk or eLance. I pay people to do this for the podcasts I am setting up on Inspiring Innovators, and it's a job that can definitely be done from your house.
