Check out the science activities link which has experiments using simple machines. The Boston Museum of Science home page has many science resources. Check out the teacher link for lesson ideas and kits available for rental dealing with simple machines. This is a place where teachers can exchange ideas and lesson plans via the internet. There are lessons for each simple machine submitted by a classroom teacher.
Teachers can request different types of lesson plans.
You can also submit some of your own lessons. Here is a page dedicated to links relating to simple machines. There are resources, activities, and LEGO projects.