If there is only one word to describe the right file format for a podcast, it certainly is "MP3." There are times when other file formats are more suitable though.
It delivers higher quality audio than MP3 codec at any comparable bit-rate.
AAC is supported on Apple platform, although plug-ins are available for other platforms as well, including Windows PC.
WMA is the format compatible with Windows operating system. MP3 typically produces better quality sound than WMA unless in low quality setting. If you audience prefer one format over another, then consider publishing in that format. I have noticed podcasters provide links to the secondary file format without feed.
