the bekvam step stool (bottom image) from ikea has always been one of my favourite designs. people are often surprised at that, but it's such a useful piece of furniture, and at such a low price, most people i know have at least one.
i noticed in the most recent ikea catalogue another addition to the bekvam range: the stepladder. it won't be as multifunctional as the step stool i'm sure, but it's still a very nicely proportioned thing, and would be very useful in it's own right. and only £29 too!
made of solid beech, it part-folds for storage. available from ikea.