Constructivism

Constructivism is a theory of learning and not really a theory of teaching/instruction. So there are several ways accounts of people trying to based teaching/instruction on "how children learn" and not necessarily one way. http://en.wikipedia.org/wiki/Constructivism_(learning_theory) if you already have not checked it out.

http://dougiamas.com/writing/constructivism.html also has a very interesting view and summary of his journey in understanding constructivism.

In any case here are some books/articles that I have used/read and found very effective and helpful.  

This book edited by Fosnot maybe a good one to read to begin to understand the basic ideas of constructivism and how teachers have tried to base their teaching on these ideas for different areas.
http://books.google.com/books?id=aEE0HgAACAAJ&dq=constructivism&ei=s-qRSeS5C5vWzAS3nfmdBg&client=firefox-a

The one for language learning that I have used and think is excellent is 
An integrated language perspective in elementary school: An action approach
by Barbara Z Kiefer, Linda S Levstik, Christine C Pappas 

Books by Fosnot are in general good for mathematics.
The Young Mathematicians at work series
http://books.google.com/books?id=Dp-eAAAACAAJ&dq=fosnot&lr=&ei=v-uRSf7MKaaGzgSchryNCg&client=firefox-a

Children's mathematics - an excellent book based on constructivist ideas for mathematics learning and teaching in the early years.
http://books.google.com/books?id=WUEJAAAACAAJ&dq=cognitively+guided+instruction&lr=&ei=_-uRSY7IEI6syASyupSFCA&client=firefox-a

The WCER group in wisconsin has some very interesting stuff for parents, teachers.
http://www.wcer.wisc.edu/archive/mims/Parent_Newsletters/index.html
They have a whole list of various projects and publications by those projects in different areas - science, math, literacy and are firmly grounded in constructivism.
http://ncisla.wceruw.org/publications/ some of which are available for downloadinghttp://ncisla.wceruw.org/publications/#articles

Thinking Mathematically: Integrating Arithmetic and Algebra in Elementary School.
Thomas P. Carpenter, Megan Loef Franke, Linda Levi
Publisher: Heinemann 2003

Investigating Real Data in the Classroom - Expanding Children's Understanding of Mathematics and Science. Richard Lehrer and Leona Schauble, editors.

Designing Learning Environments for Developing Understanding of Geometry and Space (A volume in the studies in mathematical thinking and learning series). Richard Lehrer and Daniel Chazan, editors.
Publisher: Teachers College Press, 2002. 

Book by Constance Kamii are excellent, she is sort of the authority on Piagetian constructivism and her books are very practical for math learning. I would look at the young children reinvent math series and the other one on group games.
http://books.google.com/books?q=+inauthor:%22Constance+Kamii%22&client=firefox-a&source=gbs_authrefine_t

This book by Rheta Devries looks interesting though I have not read it. But I would give it a consideration since other books of hers are helpful and useful.
http://books.google.com/books?id=UqZ9HgAACAAJ&dq=constructivism&ei=s-qRSeS5C5vWzAS3nfmdBg&client=firefox-a

This book seems to be a overview of how to create and sustain constructivist classrooms.
http://books.google.com/books?id=xN7jfzpYR7cC&printsec=frontcover&dq=a+constructivist+classroom&ei=b-mRSZ7PEaSsyAT5_KSHCg&client=firefox-a#PPP12,M1

This book is on constructivism and science, so worth a look
http://books.google.com/books?id=u2rtJ3hGmE0C&pg=PA12&dq=constructivist+teaching&ei=T-qRSaueNoSUzATlpKz1CQ&client=firefox-a#PPP1,M1

I-Anita