BlogRovR is a Firefox extension that lets you browse the web guided by your favorite blogs. After you install the extension, you'll have the opportunity to enter a list of blogs (there are also predefined bundles of blogs) or import an OPML file from your feed reader. Everytime you visit a new web page, you'll a small box with snippets from the blog posts included in your list that link to the current page. For example, if you visit Google Video, you might see two surprisingly similar posts from TechCrunch and Mashable that discuss the problem of copyright infringement in online video sites and link to
full-length movies available at Google Video:
You can configure from the toolbar how often BlogRovR's list shows up and even disable it when you don't want to see it.
This is a great way to cluster blog posts: visit the source of a news and you'll see a list of blogs that link to that page. It's also a method to see if one your favorite bloggers linked to your site.
Note: If this extension gives you a déjà vu feeling, then you know about
Blogger Web Comments, a Firefox extension created by Google that "makes it easy to see what bloggers are saying about a page you're viewing". The difference is that Google's extension doesn't let you restrict the blogosphere to your favorite blogs.