You can find the Creativity Lab’s project guides for classroom projects here.
Science Snacks A series of low-cost, high-quality science projects created by the Teacher Institute out of the Exploratorium.
Tinkering Studio The Tinkering Studio has a great set of low-bar, high ceiling projects. They all have the potential to be integrated into math and science curriculum in rich ways.
Meaningful Making A free eBook download from the FabLearn Conference out of Stanford University.
Teacher Maker Camp Cookbook The Cookbook was published by the WAAG Society Institute for Art, Science, and Technology in the Netherlands. It is a great guide and resource for exploring making in education.
Instructables There are more projects here than one person could do in a lifetime. Quality varies; we particularly like the projects by the Tinkering Studio (yep, them again!) and The Oakland Toy Lab.