LeMill is a web community for finding, authoring and sharing learning resources. First at all, you can find learning resources. The stuff you find you can use in your own teaching or learning.
What is Gabbr? Gabbr allows you to read and comment on the latest news across major news sources as well as the blogosphere. Bloggers can submit their blog posts to appear on the front page for others to comment on.
C. Lampe, N. Ellison, and C. Steinfield. Proceedings of the 2006 20th anniversary conference on Computer supported cooperative work, page 167--170. New York, NY, USA, ACM, (2006)
D. Gibson, J. Kleinberg, and P. Raghavan. Proceedings of the ninth ACM conference on Hypertext and hypermedia : links, objects, time and space---structure in hypermedia systems links, objects, time and space---structure in hypermedia systems - HYPERTEXT \textquotesingle98, ACM Press, (1998)