The TeLearn dictionary and thesaurus is a useful growing resource of information giving overviews of concepts and ideas relevant to online and technology-enhanced learning. It’s in wiki form so will hopefully grow further.
The entry pointed to by this bookmark gives one of the clearer definitions of Constructionism that I have read. I particularly like the succinct characterisation that constructionism is an operationalised pedagogical branch of Constructivism (that provides a general philosophy and set of ways of understanding how people learn, but that has little so say on the subject of how to go about improving learning). Terry Anderson and I had a question posed to us at our http://www.slideshare.net/jondron/its-hardly-easy-to-be-softly-hard-freedom-and-control-in-learning-spaces at the Networked Learning Conference in Maastricht about why we did not include Constructionism in our list of generations of distance learning and I think this answers that question well: it is one of a fairly broad set of theories that fall under the constructivist umbrella and that help to define the second generation, but it is certainly not a generation in itself.
Address of the bookmark: http://www.tel-thesaurus.net/wiki/index.php/Constructionism