Brian Benzinger over at Solution Watch has a very good and detailed write-up about the emergence of "single-page aggregators," or SPAs, Web sites that collect numerous content feeds, usually in a particular category, and display all their headlines on one page. Really these sites are just RSS readers, but their focus and clear layouts make them easy to scan.
One of the most popular of the SPAs is Popurls, which collects geek links from Digg, Reddit, Del.icio.us (all of which are also aggregators), and more than a dozen other sources. I was completely hooked on it until I found Original Signal, which collects headlines only from blogs that cover Web 2.0 news. The Original Signal folks just added a gadget page, too.
For a rundown of sites in other fields, read Brian's post. And if your interests are not in perfect synchrony with the publishers of those sites, make your own SPA with Netvibes, Pageflakes, or Webwag. (Old-school folks can also use My Yahoo, probably the most popular RSS reader out there for people who don't know what RSS is.)
For the people and companies that create the stories that these sites link to, the sites are a mixed blessing. On the one hand, just as they aggregate content, these sites can aggregate audiences, thus exposing more people to content they otherwise might not see. On the other hand, these sites also dilute these audiences, can decrease casual browsing to sites, and can reduce readers' use of RSS feeds that might have revenue-generated advertising in them.
Single-page aggregators are also giant battlefields. So many headlines in such a small space encourages vicious editorial competition. So, more work for the likes of me, and better reading for all of you.