Show HN: RSS Feed Discovery Engine
discovery.thirdplace.no
It accepts urls and tries to find a feed for it. Most of the work is O(1). Scratches a personal itch.
discovery.thirdplace.no
Also some sites don't support RSS but there are public services available that can help out. (Ex: nitter.net for Twitter.) I was talking to the author earlier and they were considering adding a "third-party" section to the response. This would allow getting feeds even for sites that don't support RSS natively.
Also as awesome as an alternate link is, the reality is that most browsers don't do anything about it these days. Even worse, the most popular browser (mobile Chrome) doesn't even support extensions that would allow adding support. So it is nice to have a nice accessible frontend for discovery. The extra heuristics are really just a bonus. (Of course if all feed readers supported discovery this wouldn't be as much of an issue but the reality is that the most popular readers don't. So lots of gaps that this tool fills)
I really need to get around to writing the article I want about how to set up a feed for your website with all of the best practices. Some day...