By now you've surely heard about Meg Hourihan and Nick Denton's Kinja,
the "public aggregator for the rest of us". It should be
pointed out that Charles and Indi's Rollup has been offering similar functionality for a while. (Example: striproll.)


Interestingly, Rollup offers a full implementation of what I've called feed splicing,
offering an RSS feed for each digest/rollup and thus making the output
amenable to other manipulations (e.g. republishing digests/rollups as
sideblogs using tools like feedroll).


If you're looking for topic feeds, also check out topix.net (here's their social software feed).
[Seb's Open Research]