It seems everyone is concerned with tracking the effectiveness of social media. We've said it before, and we'll say it again: establish specific metrics to measure your social media efforts by. There is no ticker (yet) that will magically calculate the exact financial ROI of your social media presence.
However, you CAN track certain specifics such as number of followers and level of interactions. And, with Google Analytics, you can now keep track of all the social action (such as RT's and Facebook "Likes") your website is getting.
You can find out more about Google Analytics Social Plug in Tracking here.