I have been looking at this book, Collage and Construction in School, Preschool/Junior High. The very first words in the text are "Children explore their senses with the world of simple things." Sold.
This book was published by Bank Street, and you can buy it from them. But the ideas are simple - children and adults should collect interesting materials for collage. For construction, children should also have a variety of materials that can bend and change, presenting opportunities for a variety of designs and structures. If you come across this book, though, grab it - the photographs and ideas are inspiring.
Through my searching, I found that Lois Lord also wrote a book about using plant dyes in the classroom - that one is out of print, but I'm ready to hunt for it!