The National Archives has an interesting and informative blog entitled Pieces of History. In it, primary sources are regularly highlighted. Last year they wrote about the Dunlap Broadside printed on July 4, along with the real-time proceedings of that day inscribed in volume 3 of the Rough Journal of Congressional proceedings.
This year they wrote about the Binns engraving of the Declaration of Independence that was created in the surge of nationalism following the War of 1812.
You can learn more about the Declaration of Independence at America’s Founding Documents.
The National Archives also has a wealth of resources for Independence Day.