While there is software that allows you to create an RSS feed, I recommend using Wordpress. The great thing about Wordpress (a free blogging software) is when you enter a posting (show notes) it updates your website, and adds that entry to your RSS feed.
In your entry you point to your media (mp3, or video, pdf) so that when the listener fires up their podcatching software (itunes, juice, etc), it reads the RSS, that shows the show notes, and directs them to the media that gets automatically downloaded.
So the short answer is "a Wordpress blog." You can install Wordpress with a few mouse clicks with most web hosts. My recommended host is at www.schoolofpodcasting.com/hosting Another benefit of wordpress is you can schedule shows for future delivery (so when you go on vacation your podcast continues without you).
Wordpress automatically creates the RSS feed, and automatically update its when you update your website.