Shorpy.com is a photoblog featuring high-definition images from the first half of the 20th century. The site is named after Shorpy Higginbotham, a boy who worked in an Alabama coal mine and ironworks in the 1910s.
Many great old and artistics photos we can find there. Here are two examples:
Gotham City: 1910: “Fifth Avenue and Forty-Second Street, New York.” Circa 1910, horses and motorcars shared the streets. Detroit Publishing glass negative.
The Washboard Jungle: 1900: “New York tenement yard c. 1900-10.” One of the better surviving images of turn of the century tenement life. Detroit Publishing glass negative.
If you like photography, art or even history, Shorpy is a great site to visit.