Chem Exam Page: Not exactly lesson plans, but there are nearly forty chemistry exams and quizzes available for download in pdf format.
Chemistry I Index: Chemistry I resources, mainly demonstrations and labs. Includes some teaching tips, exercises and handouts.
Chemistry II Index: Chemistry II resources, mostly labs.
Chemistry Lesson Plans, from the SMILE Project: About 200 lesson plans.
Middle School Science Lesson Plans: Includes number of lesson plans in chemistry.
Salt, the Essence of Life: A Multidisciplinary Curriculum for Students: Salt, sodium chloride, can be used to teach many subjects. The Salt Institute has prepared this high school curriculum for teachers, but students can use it independently.