The only thing that I can remember is something called Cal-Ban 3000, which was horsepills containing guar gum. When you took them as recommended, with 8 oz. of water, they would swell in the stomach causing fullness. Unfortunately, they were sued for this same effect, when some people got the pills caught in their throats, where they swoll up causing asphixiation.
I remember reading on the back of a bottle and it instructed you to take up to 20 pills a day. And these bastards where big and chalky, not something that would swallow easily.
Acarbose, as another poster mentioned, is the only carb-blocker ever used clinically, but I know that it is still used.