I've made a new relay computer: check out
formatting link
(look for the videos on the example programs page).This one is a single board computer, like the microprocessor trainers of the
70s and 80s.
A trick to keep the relay count very low is my design for a master-slave flip-flop. By using a capacitor for the master side and a holding resistor based latch for the slave side, only 1.5 relays per bit are needed.