Middle/Secondary Lesson Resources

If you want students in your class to hear from scientists about their work, check out this site.
Skype a Scientist
https://www.skypeascientist.com/

For a focus on the nature of science and how scientists do their work, check out this site.
Understanding Science
https://undsci.berkeley.edu/

There is a wealth of high-quality, ready-made science lessons on the web. Here are sites that encompass a wide range of science topics.

PBS Learning Media: Science
https://vpm.pbslearningmedia.org/subjects/science/

National Museum of Natural History Teaching Resources
https://naturalhistory.si.edu/education/teaching-resources

Science in the City Resources
https://scienceinthecity.stanford.edu/resources/

Exploratorium: Digital Teaching Boxes
https://www.exploratorium.edu/education/teacher-institute/digital-teaching-boxes

California Academy of Sciences Lesson Plans
https://www.calacademy.org/educators/lesson-plans

HowtoSMILE.org
https://www.howtosmile.org/

National Science Foundation Classroom Resources
https://www.nsf.gov/news/classroom/

NOVA Labs
https://www.pbs.org/wgbh/nova/labs/

CK-12 Teacher
https://www.ck12.org/teacher/

National Park Service Educator Resources - Search by subject and grade level
https://www.nps.gov/teachers/index.htm

Smithsonian Educator Resources: Science and Nature
https://www.si.edu/educators/science-resources

Here are some sites that offer detailed lesson plans and guidelines for hands-on activities. They are grouped loosely by discipline.

Life Science

BioEd Online Lessons and More
https://www.bioedonline.org/lessons-and-more/

BioInteractive
https://www.biointeractive.org/

Teach Genetics
https://teach.genetics.utah.edu/

The Biology Corner
https://www.biologycorner.com/

Understanding Evolution
https://evolution.berkeley.edu/

Earth and Space Science

Infiniscope
https://infiniscope.org/

Earth Exploration Toolbook
https://serc.carleton.edu/eet/index.html

Teaching Climate
https://www.climate.gov/teaching

Teach the Earth
https://serc.carleton.edu/teachearth/index.html

Kinesthetic Astronomy
https://www.spacescience.org/eduresources/kinesthetic.php

USGS Educational Resources
https://www.usgs.gov/educational-resources

NOAA Ocean Exploration Education Resources
https://oceanexplorer.noaa.gov/edu/welcome.html

NOAA Resources for Educators
https://oceanservice.noaa.gov/education/for-educators.html

NASA Resources for Educators 5-8
https://www.nasa.gov/learning-resources/for-educators/for-educators-grades-5-8/

NASA Resources for Educators 9-12
https://www.nasa.gov/learning-resources/for-educators/for-educators-grades-9-12/

Physical Science

Inquiry in Action - Grade 5 Lessons
https://www.acs.org/education/resources/k-8/inquiryinaction/fifth-grade.html

Middle School Chemistry (NGSS-aligned lessons)
https://www.acs.org/middleschoolchemistry.html

Celebrating Chemistry
https://www.acs.org/education/outreach/celebrating-chemistry-editions.html

Periodic Videos
http://www.periodicvideos.com/

Jefferson Lab Teacher Resources - You'll find not only activity ideas but also videos, games, worksheets, puzzles, and more.
https://education.jlab.org/indexpages/teachers.html

The Science Explorer
http://www.exploratorium.edu/science_explorer/

PhET: Interactive Simulations
https://phet.colorado.edu/

Universe & More: Interactive Physics Resources
https://universeandmore.com/

Engineering

The Concord Consortium
https://learn.concord.org/

TeachEngineering
https://www.teachengineering.org/

Try Engineering
https://tryengineering.org/