(1) "The British Journal of Sociology" (vol. 65, no. 4, 2014) features a symposium on Thomas Piketty's "Capital in the Twenty-First Century" (Belknap Press, 2014), including Piketty's response:
The papers can be downloaded for free.
(2) A panel discussion of Piketty's book at a meeting of the American Economic Association, January 3, 2015.
A video of the presentations and the discussion here. And papers here.
Thomas Piketty - "About Capital in the 21th Century" (pdf)
See also my links to reviews of Thomas Piketty's book here.