http://school.discoveryeducation.com/lessonplans/
Can search by subject or grade level.
http://www.nytimes.com/learning/teachers/index.html
hundreds of free lesson plans for grades 6-12.
Multi-media resources and lesson plans. Click on the left side bar for standards-based resources.
http://www.nationalgeographic.com/education/
Lesson plans, classroom activities and more.
http://www.archives.gov/education/index.html
Teaching with Documents Lesson Plans contains reproducible copies of primary documents related to U.S. History. Lesson plans include the documents, links to standards, teaching activities, and worksheets.
http://www.sdcoe.k12.ca.us/SCORE/cyberguide.html
Links to lesson plans for primarily languages arts with some world languages.
http://memory.loc.gov/ammem/ndlpedu/index.html
U.S. History, civics and literature lesson plans.
http://www.readwritethink.org/lessons/index.asp
International Reading Association Site. Detailed lesson plans with links to resources. Can sort lessons by grade or title of lesson.