Right now, I use Google Reader for keeping up with RSS feeds, and so far, it seems to be the best featureset out there. If you like, you can read all feeds in chronological "River" view, as Dave Winer prefers, or you can organize them by folders, or even read each folder by chrono, if you like...
...but what I *really* want a reader to do is to embrace something that I think falls best between OpenID and OpenSocial, where each entity (person/business/organization, etc.) has an identity, and they can tag each of their other info-streams with this tag, and follow it back to the root identity for attribution, as well as to discover other tasty morsels of info-goodness that the identity may also publish.
I follow PersonX on Twitter.
They refer to a clever Twitter by one of their friends, so I go look at that.
I decide that FriendX is pretty interesting, so I "follow" them on Twitter.
Here's where this new layer would come in...
Twitter includes a link to FriendX's ENTITY info, which is just a bit of RDF giving their basic info, and links to any other bits of info they publish publically.
I see from FriendX's entity info that she's also got a blog, a Seesmic feed, and a Flickr page shared.
I browse these, and decide to subscribe to her blog as well.
Google Reader would know about this Entity info also, and offer the ability to not just group different RSS feeds by folder, but also by Entity, allowing me to read all streams from the one Entity in one info-ball if I like, and sort my daily reading much better.
Does this already exist in a form I just missed? Anybody doing it yet?
Seems like it'd be useful and fun.
UPDATE: MissRogue just mentioned DataPortability.org (which I've looked at briefly, but need to take a closer look at to see if they've got the aspects I'm looking for here) as potential overlap. Good stuff!