http://www.8bitforce.com/projects/retroshield/
There were (are?) boards for driving a Z80, 8085, and a couple of other processors all via an Arduino-Mega.
It was a fun project which later lead to me working on a simple single-board Z80-based system, and that lead to me playing around with CP/M and similar things.
But it is dead: https://web.archive.org/web/20180512095336/http://www.hackin...