GBCartRead is an arduino based original Gameboy cartridge reader made by Alex at inside gadgets.
I am a huge fan of retro video games and have quite a collection of gameboy consoles and cartridges myself. I have wanted to make a cart reader / writer for a while now but have just not had the time to even start such a project.
Alex has done exactly that though and includes a great write up on his site as to how the gameboy cartridges work and how he went about interfacing it to an Arduino in order read the cartridges contents.
Found via hackaday.