YackTrack is a web service that lets you search for comments on your content from various sources or other blogs that talk about your content. Just enter a URL of your blog post, and it will return every comment on that URL that it can find across multiple servicesfrom just one location. While helping the content producer, it can also help the people commenting on the content themselves. If you have commented on a blog post, you can find other people that are commenting on the post and join the conversation on other sites.
YackTrack currently supports Blogger/Blogspot, Digg, Disqus, FriendFeed, Google Blog Search, Google Reader, IntenseDebate, Mixx, Reddit, StumbleUpon, Technorati, TypePad/MoveableType and WordPress blogs. Obviously, this list should expand as the site continues to grow.
More info: YackTrack