By filtering your results by popularity, you'll be able to pare down a bunch of results that are presumably all relevant into the top sites on your topic, or some surprising ones you might not have heard of.
Love Digg's RSS feed but don't have time to keep up with it all? Disstill is like your regular Digg RSS feed but filters out stories below the minimum diggs that you set.
PostRank claims to measure social engagement, including blog posts responding to someone else, bookmarking an article, leaving a comment on a blog, or clicking a link to read a news item.
Adobe AIR app that lets you display items in your RSS feeds in a scrolling ticker on any edge of your screen. Not for the faint of heart or the information averse.
APML allows users to share their own personal Attention Profile in much the same way that OPML allows the exchange of reading lists between News Readers.