DON'T LET THIS THREAD DIE! These are really good tutorials and I hope you will continue to make more. I'm currently working on my own ALU right now using your instructions, and RedPower.
P.S. I was too lazy to actualy make an adder, so I made a truth table instead using redpower array, It goes through each combination to check if the output is 1 or 0, then it checks again to see if it's 10 (or 11) or 0(or1).
Also, I'm wondering, does adding multiples of the same function to the ALU make it any faster or able to compute more things at once?