Simple PHP script which generates an RSS feed from all files in directory. The generated feed can be imported into your favorite podcast client. So if you occasionally want to download a certain episode from a podcast show, without having to subscribe to that show, simply copy the downloaded mp3 into the PodcastFeed-directory and after a while, the file is ready to play in your podcast app on your iPhone/Android phone.
Additional tip: mount a Bittorrent Sync or Dropbox folder to the directory where you have put the index.php file. This way you can easily add podcast shows to your "custom podcast feed" by copying them into the folder.