Time needed: ~ 1 hour

Klout is a service that uses social media analytics to rank its users according to online social influence via the "Klout Score", which is a numerical value between 1 and 100. In determining the user score, Klout measures the size of a user's social media network and correlates the content created to measure how other users interact with that content. In other words, Klout shows you which people are the most influential on social media in a given topic.

First, register at Klout dev center http://developer.klout.com/ in order to obtain Klout API key. You fill in a short form, and you get a key instantly.