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.
The challenge for Friendfeed and the like is that while I really like all my services gathered in one place, I would rather that these would be centralized on my blog instead of a third party service. Yes you can cross post or add badges, but it's not rea