Good ole Francesco points out that the first ever homebrew cart has been released for the Creativision, a 1981 European game console/computer. Only 100 were produced, which is good, considering the thing costs about $58. Anyway, it's being released on September 30th by these dudes in Italy, called Madrigal Design, who also make the Creativision emulator. The official page for the homebrew cart is here, and features all the original Creativision games and programs (making it a bit grey market), and comes with a manual for all games, some controller inserts, and other various stuff. Give it a look