Bruce - you can buy digital scales, (recommended), or you can buy scales the weigh everything from grams to pounds. If you want to weigh small lizards or snakes, I'd go with a tiny dig. Beware, however, they can get quite costly! Cheapest ones I've seen are probably around a hundred bucks here!
(P.S. Don't ask me why I know so much about scales... J/K) =D