MESS covers an awful lot of consoles. It's intimately related to MAME (takes advantage of the fact that MAME already emulates about every processor under the sun) and might be worth a port if i finish implementing the arm bits MAME needs for optimal performance.

BTW if anyone wants to make up a new/better/regularly updated emulators thread, i'll link to it in the sticky. This one has been rather neglected. A fine alternative would be a wiki page.