Klout offers an attractive application to measure your social network influence. They consider your true reach, according to several content questions; your amplification influence, with subcategories including engagement; Network influence, by paying attention to all the effects your tweets or messages had in different contexts. They also offer different widgets for developers.
This is quite an interesting tool, because we all know it´s not the same to “shout”, “talk” or “engage” on the net. They also have a blog, which offers forst hand opinions and ways of becoming an active and interesting voice in the internet sea. Content (still) matters.
Their site is: http://klout.com/home