I was reading a new book I checked out from the library called Mediapedia by Kit Laybourne and found some great resources that were highlighted in the back of the book. One resource that really fascinated me was one for the Library of Congress Digital Collection (click here for collection).
Wow, what an amazing resource. I stumbled upon old baseball songsheets and a massive collection of prints and photographs. The amazing thing is that you can download some decent high resolution pictures for free.
They also provide a web archive of The Library of Congress which is really amazing to check out. They have the web archive from 9/11 which is a great resource for all.