Nicholas Chim's Personal Bee project is some confirmation that a lot of what I've been thinking about in terms of aggregators isn't out in left field. The Bee watches bunches of feeds, does some term analysis of the items that come across a bunch, and generates a tagcloud for navigating the items. TechCrunch has a good overview, but it's something like a personal scale Google News.
Lots of mileage in this idea.