The Biodiversity Heritage Library is an online website that makes biodiversity literature openly available in order to help improve research methodology. 

The CaseLaw Access Project is an online website that includes all official, book-published state and federal United States case law. It is an interactive website of the United States where you can click on each individual state and see the cases that occurred there. 

The David Rumsey Map Collection is a website dedicated to David Ramsey's map collection that he has been collecting over the past 35 years. The collection focuses on a multitude of maps from the 16th through 21st century from areas including North and South America, as well as Asia, Africa, Europe, and Oceania. The collection has several types of maps, including atlases, globes, wall maps, pocket maps, books of exploration, maritime charts, and manuscript maps.

The collection began digitization in 1996 and now there are over 119,000 items online, with the website being updated regularly. The site is accessible to the public. Viewers are able to utilize a variety of tools that allow users to compare, analyze, and view items.

The Digital Public Library of America (DPLA) provides freely available resources from America’s libraries, archives, and museums. You can find many primary sources here from different time periods and on different subjects. Go to their Primary Source Sets to either search or browse sources by topic.

See DPLA's help page for more information on how to search and browse the collection.

DPLA's Primary Source Sets are designed to help students develop critical thinking skills by exploring topics in history, literature, and culture through primary sources. Drawing online materials from libraries, archives, and museums across the United States, the sets use letters, photographs, posters, oral histories, video clips, sheet music, and more. Each set includes a topic overview, ten to fifteen primary sources, links to related resources, and a teaching guide.

Europeana is a European digital library which gives access to online collections of many Europeans institutions (archives, libraries, museums). You can search the catalog for newspapers by title or by period.

HathiTrust is an online collection of books published before 1923. Many of these can be viewed online in their entirety, and others can be searched for keywords.

The Wayback Machine has archived billions web pages from 1996 to the present and lets you view old versions of websites, even those that no longer exist. The Wayback Machine is part of the Internet Archive, which is a non-profit library of millions of free books, movies, software, music, websites, and more.

The Library of Congress has over 300 digital collections that include books, maps, manuscripts, photos, records, newspapers, drawings, and many other rich materials. 

The National Archives contains a webpage titled "Finding Primary Sources for Teachers and Students" on different open access primary source sites for teachers and students to utilize in their work. 

Smithsonian Open Access is a resources that provides access to almost 3 million digital items from their collection from 19 different libraries. Search for and learn about different paintings, objects, animals, statues, and many more rich items that they have. 

Provided by the Library of Congress, the World Digital Library works with libraries, archives, museums, educational institutions, and international organizations from around the world to have primary sources from all countries and cultures.