Hey, I made a binary calculator using redstone. Basically you flick some levers and then addition is done within the redstone and then comes out as a 4-torch display at the front. Because it is binary, one of the torches is worth 1, the next is 2, then 4 and then 8. I'll send the download link out after it's fully complete, but I plan to make it count up to 256, which would need 7 calculators, and at the moment I have 4. If I get good enough feedback I might even make a display you see on a normal calculator! :O

Look forward to your feedback,

-Piggy.