Incorporating primary sources can be an informative and interesting way to instruct students on different subjects. Some of the resources listed in Resources for Building Lesson Plans already utilize primary sources, but you can find your own by using some of the resources listed here.
Some resources listed here were found through Edutopia: Five-Minute Film Festival.
Librarian Tip: Many museums will have educator resources for specific artwork in their collection. Studying a piece of art or an artist held in a particular museum? Check out their page to see if they have resources for you.