This one's a third party deal. It's called GetKudos.
https://getkudos.me/Very new, and still a little wet behind the ears but it's free and seems to work. It actually can be used on any site where you have the access to the code.
It can be set up to draw in mentions on Twitter and Facebook, reviews made on site via the widget, and custom reviews you create (I created one with a link to my Etsy reviews). They all go to a dashboard where you can decide which ones you want to make public.
It's not perfect. If you get a lot of mentions you have to sift through them for the relevant ones. What I like best about it, though is that it doesn't hound your customers to leave reviews (as in it doesn't send them an email after they make a purchase). If they liked their purchase enough to return to the site - even months later - they can leave a review, then, if they wish.
I have the floating widget. You can see it here:
http://croweshea.mysupadupa.com Like I said I don't have any real reviews, yet.