In the past Sony released a special PS1 that you could develop games on called Yaroze. It started the careers of a few hobbyists and a game for it, Devil Dice, ended up getting a retail release (http://en.wikipedia.org/wiki/Devil_Dice).

The Japan only Bandai Wonderswan had a homebrew system as well, named Wonder Witch. "Judgement Silversword" was published at retail for the Wonderswan but produced originally via this homebrew system and it is considered to be one of the best games for the platform.