There are places to find lesson plans, of varying quality, all over the internet. Lesson plans that explicitly incorporate primary sources and primary source exploration are rarer.
Stanford History Education Group
This is an excellent site, and its Reading Like a Historian section is full of great lessons for a variety of ages, particularly middle and high school.
Library of Congress
There are wonderful sites within the Library on the its resources and on how to teach using primary sources. The main Teachers page provides primary source “sets” that are searchable by grade and type of standard (Common Core, state, and organization) as well as a page that summarizes questions to ask with students. The Teaching With Primary Sources section focuses on how to use the collections of theLibrary in the classroom, primarily through the TPS Journal, which contains excellent articles about teaching with primary sources.
Digital Public Library
Digital Public Library is a collection of primary sources grouped by subject matter. But it’s on this Online Lessons page because their Primary Source Sets also have teaching guides which you can use for a complete lesson. A great variety of US history sources. Not a huge amount of World History, but that might change. Sorry Ancient History and contemporary world events folks, nothing here for you at the moment.
TPS—Barat Primary Source Nexus
This is a free professional development site connected to the Library of Congress, Teaching with Primary Sources. It provides lesson ideas and plans, tips, a blog and more. There is good content for a variety of levels, but it’s probably most useful for grades 5−12.
National Archives Experience
The Docs Teach section provides lesson plans using primary sources from the National Archives. The Teacher’s Resources section provides links for educators. The “Special Topics and Tools” page provides links to a few National Archives e-books.
Smithsonian-Engaging Students with Primary Sources
This is a pdf by the National Museum of American History,Kenneth E. Behring Center with lessons plans and students worksheets focusing on types of primary sources, such as photographs, newspapers, and oral histories.
Smithsonian Source, Resources for Teaching American History
This site provides videos, a few lesson plans and DBQ activities in six categories, ranging from Colonial America to Inventions. It also provides links to stand-alone primary sources from the Smithsonian collection, but the site is very small and does not give the user access to all the Smithsonian’s many primary source items.
Primary Source—Resources, Online Curriculum
This site provides lesson plans using primary sources about different parts of the world and world history. Most are for higher grades, but a few are specifically aimed at elementary students.