Over at ASM Retro they've created a reproduction of the classic Gameboys test cartridge, something that was only available to certified repair centers and as such they're pretty hard to find today. The first batch of carts is $15.99 each and can be ordered here.
http://asmretro.com/testcart
This is not paid advertisement, but a release I think is cool... the Gameboy isn't getting a lot of love homebrew/reproduction wise these days :-/
http://www.nesworld.com/
