One of the things I love most about photography is its rich history of innovation and quirkiness, with a vast range of cameras and lenses with unique designs having come and gone throughout the years. If you would like to take a trip down memory lane (or you need a manual for that old camera sitting on your shelf), this fantastic site features a wide range of camera and lens manuals and sales brochures from about 120 different brands across decades of history.
One of my favorite hobbies is collecting vintage cameras and playing with them. Some of them, like my Argus C3, are not particular notable for their functions or image quality, but they simply look cool and sit on my bookshelf. Others, like my Rollei 35SE or my Fuji GW690 III see regular usage. The Rollei 35SE is a unique, bizarre, and ridiculously fun camera to shoot with, while the Fuji GW690 III features a sharp lens and gives you absolutely massive 6x9 negatives, the combination of which led to photographers to affectionately refer to it as the "Texas Leica." Perusing these old sales brochures is a great way to see what had photographers excited back in the day.
Check out Pacific Rim Camera to see the full collection.