CoComment
One of the really bad things in the blogosphere is keeping track of all the comments you made around other blogs. And if you use a news reader to aggregate the RSS feeds, it’s even worse, because you don’t even see any comments - unless you visit the blog in your web browser.
Enter CoComment by a team of Swisscom Innovations. Laurent Haug also has his fingers in it somehow. This application keeps track of the comments you posted and comments to your comments. It integrates as a bookmarklet, but Firefox users can take advantage of a Greasemonkey script to handle the really difficult taks of hitting a bookmark prior to posting.
Great stuff, highly recommended. So far, in private beta and requires invitation. I have two codes to share, first two commenters asking for one will get it by email