I get all my stuff from [romsite name redacted]. It's a ratio torrent site, and the mods can be really harsh, but behave and the classics are your oyster, or, the world is your emulation (or something).
They have all the mame roms and art files, old amiga, intellivision, colecovision, atari, tandy, DOS, saturn, daphne, whatever (look under TOSEC). Sony and Ninty are a sin - don't even bring it up.
Circo used to post his AVI packs, but there were some problems with DATs and I don't think he's done it in a while.
I'm not affiliated other than being a member. It's just been a great place for anything I've needed (wanted) for many years.