With the world awash in content, filtering is the great problem of the age for all of us. Arguably, the online social revolution is just a means to this end -- our friends are just another way we filter the information we choose to consume.
Early in 2010 I wrote about Darwin Ecosystem, an advanced new filtering service for helping you pick out news themes and trends emerging from the digital content fire hose. Bill Ives (@billives) posts here about new "themed" editions of this service, which, though scoped down in terms of the sources each spiders, are both full-featured and free to try.
My earlier post explains the service and its significance in detail, but you might just try it first, then go back and read the manual!