Mojikan is a new site that aims to introduce a new concept of interactive tools for online social behavior. They are still heavily involved with their site development, but you can still explore parts of their site, and see what they plan to offer.
L. Denoue, J. Adcock, S. Carter, P. Chui, and F. Chen. Proceedings of the 10th ACM symposium on Document engineering - DocEng '10, page 235. Manchester, United Kingdom, ACM Press, (2010)