I was going to make an ALU with my adder, my XOR/AND logic card (which I was still working on), and a ton of other relay-consuming parts. Then I did some research on how best to wire all these parts together and found a 1-bit, 9-relay, 128-function ALU.
Although many of these functions are useless or unknown, a 8-bit version would be many times more powerful than my ALU design, and probably use less than half of the relays.
The eight switches tell the ALU which function to run. The two small switches on the right side of the breadboard are A and B inputs. Red LED is the result, small green LED in the left is the carry out.