I'm using Action Streams for a blogroll using the "website" service.
However, some sites on my blogroll don't have a "discoverable Atom or RSS feed"; they have feeds, but for whatever reason they're not in the header or address bar.
Is there an existing service one can use to add a specific RSS feed, rather than the website on which the RSS feed appears? Or a plugin one can use?
I'm a little surprised that there isn't a generic RSS service similar to the website service.
I think I have tried to add RSS feeds to the website service with no luck.
Reported on Movable Type 4.25

I just had this same problem and, yeah, the website service doesn't do a great job dealing with feeds.
I wrote a rudimentary Atom feed reader Action Stream plugin, which is almost, but not quite, ready for release. It accepts an absolute path to the feed and parses it into some fields to access via ActionStreamVar.
You might want to look at the YourBlog plugin here:
http://www.openparenthesis.org/code/mtas
Jason: I look forward to seeing the finished plugin.
Does it, like the website service, allow for multiple instances?