Great primary source resources
The Library of Congress website delivers the quality of primary sources you would expect from one of the leading repositories of information. They have done a wonderful job of adding tools and resources for elementary through high school students. You can see that they are constantly adding new materials and creating content to make history more appealing to all students. I try to teach to the five senses and the resources here engage the students senses of site and sound (feel too if you print the pictures or documents).
How I Use It
The Library of Congress website is full of primary source materials that can be used to meet Common Core literacy standards. They offer non-fiction pieces that can be used to introduce topics by asking students to analyze a photograph or short exert from a document. Documents can be used to scaffold learning by going deeper into the topic. When studying the New Deal my students used photographs taken by Farm Security Administration Photographers to analyze what was happening in America during 1930's. From these images students could hypothesize about conditions in America and its people. We would then use other primary source documents to support or refute these hypotheses.
The site contains information for most topics that you would seek information. With so much information it is imperative that you use key words to refine your searches. There are many other useful tools such as Everyday History and Everyday Mysteries that can add some interest to your class. The site is also great for research projects that are student led.