The Sega Dreamcast and Sony Playstation both have, or are have in development, flash cart type devices. For those that do not know what a flash cart is, these are devices that have some memory onboard and hold homebrew games. The flash cart is seen by the console as it would see whatever format it uses, usually with a menu system of some sort for multiple games on one cartridge. The Sega Saturn, notoriously hard to program for and emulate, is now getting a flash cart of its own, at least one is in development.
Known as Saroo, the Saturn flash cart is still early in development.