So, how does it work? I recommend you take a look at the Gameboy Camera Tutorial that gwem made. It describes the easiest way to get the pictures over to a PC. Required is a device to read regular Gameboy cartridges which can be a bit expensive but also works very fast and easy.
To decode the data into pictures, use one of these programs:
gb_cam_dump saves all images as BMP. Gh0st Camera allows to save pictures as GIF, but they are not compressed so the file size is the same as the BMP’s. Also with Gh0st Camera, the greys appear a bit too dark, but that may be personal taste.
The other way to get the pictures is by Gameboy Printer emulation. Your PC then pretends to be a gameboy printer and receives the pictures from the Gameboy Camera through the print option.
This also transfers the images’s borders which is an advantage over the cartridge readers. Also it is very cheap as you do not need any more devices. Disadvantage is that you have to build a custom cable to connect Gameboy and PC.
I mirror the Gameboy Printer emulation by Matrin Eyre here, although i have never tried it myself: