A to Z Teacher Stuff has an excellent selection of The Lorax lesson plans, worksheets, and printables. There are Lorax pledge posters, Lorax worksheets, and Truffula Trees crafts.
And Apples 4 the Teacher also has an extensive collection of The Lorax lesson plans, printables, and worksheets. There is a Lorax printable maze, Lorax counting worksheets and more.
And from The Alliance to Save Energy, a 45 minute The Lorax lesson plan for 3rd grade elementary students. This Lorax lesson plan has students discuss energy conservation and create a collage from old magazines.