I remember seeing the very first photo taken in human history in a book about history of photography some two years back and it had left me a deep impression. Taken in the early 19th century (almost two hundred years ago), it actually amazes me how photography have existed since so long ago- images taken on a pewter plate.
Read more about History of Photography over at National Geographic's website.
National Geographic website and magazines are a good source of photos and an excellent read. Hahaha I've an archive of Nat Geo mags from as early as 1980!
Bookmark this page for future readings- National Geographic Photography