comp.emulators.apple2 - join
Emulators of Apple // systems.
Low activity, 142 subscribers, Usenet

comp.sys.atari.8bit - join
Discussion about 8 bit Atari micros.
Low activity, 263 subscribers, Usenet

comp.sys.sinclair - join
Sinclair computers, eg. the ZX81, Spectrum and QL.
Low activity, 416 subscribers, Usenet