How do you see their differences?

Piaget concerned with the cognitive structure, to start from known to unknown and to find relevant connections between knowledge inside classrooms and its applications outside the school. Vygotsky has two main domain of the concept, the first is the cognitive constructivism which very closed to Piaget and the second is the social constructivism which investigate the importance of building concepts and acquiring skills in a social context that gives the learner proper help in the right time which so-called scaffolding process and it suppose that the learner can obtain knowledge and skills from the teacher and class-mate better than depending only on himself without hints. Vygotsky and others referred to one reaction when student receive proper hint in the right time which called Aha reaction and then he/she can build on that hint to reach the targeted goals step by step (Scaffolding).

Good summary, Hussein Abdelfatah

Novak and Gowan, Learning How to Learn  uses a range of these cognitive structures. 

I actively use the scafolding idea in my public international law course.  Small steps, different aspects of writing and thinking about the subject.  All leading to a big moot court problem.  Today they turn in written midterms on a hypothetical problem.  Next assigment has them decide the best arguments for each side of the big moot problem. Then the draft memorial, then the oralist part, then a final draft.  And there were little assignments to check comprehension.  Works really well in that context.

Dear Vijay, the embedded link, reflecting publications since 2012, may also guide the discussion.

https://scholar.google.co.za/scholar?as_ylo=2012&q=Vygotsky+and+constructivism+and+Piaget&hl=en&as_sdt=0,5

I too have found Piagetian taxonomy to be useful.  I've also been involved in a research project that failed to confirm Vygotsky"s idea about proximal development.  See the last paragraph of the Conclusions section to this paper:

http://www.upscale.utoronto.ca/PVB/Harrison/EffectiveTeams/EffectiveTeams.pdf

I too have found Piagetian taxonomy to be useful.  I've also been involved in a research project that failed to confirm Vygotsky"s idea about proximal development.  See the last paragraph of the Conclusions section to this paper:

http://www.upscale.utoronto.ca/PVB/Harrison/EffectiveTeams/EffectiveTeams.pdf

thank you everyone, good leads

Though the concept of Vygotsky's constructivism branches out from Piaget's cognitive science.  The only difference is Piaget believed that development precedes learning, while Vygotsky believed that social learning precedes development.

I'm not sure that I completely agree with Reynaldo.  Piaget was about the individual, and Vygotsky concentrated more on the reasonable idea that knowledge is a social construct, so we seem to agree on that.  However, Vygotsky was required to work within dialectical materialism, or risk suffering the same fate as the biologists who defied Lysenko in favour of genetics, i.e. getting sent to Siberia or worse. In my opinion,  this had a sad impact on his ground-breaking thing about learning.