The idea of a feed file has been mentioned a couple of times, but no-one seems to have picked up on the obvious benefits of using a file with the rss details in it. Think of how a playlist (PLS) file works. The file can contain one or more song filenames, or a shoutcast broadcast url. The advantage is that the playlist file remains static, while the stuff it is pointing to changes.
Think of a .feed file — you’d need to register the Mime type on the server, but this is always the way of things, and it is much easier to fix than to fix all the clients out there. Once upon a time htm files were not served correctly, because they did not match the default extension mappings. PNG files also need the mime type added, and the universe hasn’t rejected them because of the mime type issues. A feed file would be an XML file containing the locations of one or more RSS feeds, along with a suggested action.
Of course, the helper app that handles .feed files should ask the user before removing or adding any feeds from the file, but the user now has to answer yes/no instead of knowing where to copy the URL from.
This solution has the advantage of being roughly as simple as the RSS feed itself, and fairly easy to understand. It’s a file you create once and then forget about.