Resource #1
Smile Program Physics Index
SMILE stands for Science and Mathematics Initiative for Learning Enhancement. It was designed to assist in the teaching of elementary and high school math and science. This web site has close to 200 lesson plans on matter, mechanics, fluids, electricity and magnetism, and waves.
Resource #2
Teach-nology: the web portal for teachers
If you can ignore the annoying advertisements at the top of the page, this is really a useful web site. It has links to lesson plans on electricity and magnetism, light and color, fluids, matter, mechanics, and sound waves and optics. The nice thing about this site is that many of the labs provided can be done using common materials. For example, for the static electricity investigation, all students need are balloons.