I basically agree with Henry, but I think that constructionism as currently practiced has more roots than just Berger and Luckman. In particular, the current constructivst movement in grounded theory (e.g., Charmaz)  traces its origins to Mead' symbolic interactionism. 

From a U.S. point of view, as a sociological social psychologist, I have always been intrigued by Moscovici's ideas, but they have never received much attention on this side of the water.

Under my perspective social representations are an instance of social constructionism, the latter meant in a broad sense of epistemological commitment. Social representations as formulated by Moscovici, do draw from the insights of Berger & Luckman and Foucault. They seek to individualize macro-sociological level of ideologies as implemented in individual minds, and relate reasoning, attitudes, and other instances of individual and social cognition to those broader structures. In this respect they embrace both quantitative and qualitative research methods. Some prominent scholars on social representations work extensively in a factor-analytical and experimental methodology, which was crystallized in the 1970's by Doise and others. Others, such as Flament, Codol, work in a highly mathematicized framework, employing graph theory and associative networks in order to capture the social representations. Perhaps these two aspects, quantification and focus on individual cognition (even though the latter is explained in terms of social constructions and social interactions) has caused a number of marxist social constructionists, such as Parker, to accuse social representations of being reductionist on the individual and cognitive level. This criticism is the special topic of the 3(2) issue of Papers in Social Representations. The relation of social representations to social constructionism is also discussed in the special issue 26(2) of The Journal for the Theory of Social Behavior. Nevertheless, keep in mind that the stance taken by Parker is not the only social constructionist perspective on social representations. For example Teun van Dijk, a founder of Critical Discourse Analysis, embeds effortlessly mental models, cognitive functioning and social representations in a critical discourse analytic framework.

Put simply, social constructionism is the interpretation and appropriation of social representations. The transformation of the shared knowledge/ beliefs/ metaphors(social representations) into everyday practices (see Howarth, 2006; Moscovici, 1988)

Virginia Mwangni, note that Moscovici is not a social constructionist per se. His writing focuses on "social representation" rather than construction. There are many common features, but also some subtle and some more blunt differences. Jonathan Potter has written about the differences between the two positions, primarily from the stance of discursive psychology, which is one of the more extreme approaches to social constructionism (ethnomethodology). 

I agree that Moscovici focuses on social representation. He however notes that srs impact on reality hence my summary above