I was just chatting with a friend and an idea came up that I have been thinking about for a few days: an email to RSS converter. This service would let you subscribe to an email newsletter via email and then send all posts from that newsletter into an RSS feed.
For this service to work, one would first need to set up an email account with programmatic access. The exact details would depend on what email provider you used. I am sure Gmail has some kind of programmatic API that would let you read emails. You could then scan for a specific recipient from which you expect an email. Then, you could extract the content of the email and turn it into an RSS feed. If you could read the raw email, this shouldn't be to difficult. Email headers are plain text and thus should be quite easy to manipulate. There are probably email parsers already.
Because emails come with unsubscribe links, there wouldn't be any need to have an extensive management interface. You could just have an email address to which you subscribe to newsletters. A simple web page or server could let you control what emails should be forwarded to the list. This would ensure no spam emails or marketing emails from other addresses get into your list.
My itch to have a service where I can forward an email to an RSS feed came up yesterday. I saw an interesting email newsletter but I wanted it in my feed reader, not in my emails. But, I could not find a link to any RSS feed that I could follow.
I don't know if there are any well-developed services out there that do this already. If so, I would love to know what those services are. I don't know how complex it would be to build something like this. My email provider doesn't have an API so I would probably need to use a service like Gmail and consume their API (unless I wanted to set up an email server but I don't want to do that!).