Pretty much every Dec and IBM machine up until the 80s.
Bitsavers has the documentation for the PDP-11/40 I used to have here. http://www.bitsavers.org/pdf/dec/pdp11/1140/. It includes microcode listings both assembled and as flow charts. My PDP-11 had actually been modified before I got it with the microcode ROMs in ZIF sockets, as someone had been writing their own microcode.
Bitsavers has the documentation for the PDP-11/40 I used to have here. http://www.bitsavers.org/pdf/dec/pdp11/1140/. It includes microcode listings both assembled and as flow charts. My PDP-11 had actually been modified before I got it with the microcode ROMs in ZIF sockets, as someone had been writing their own microcode.