I'm assuming that when one showers / bathes and uses a bar of soap but isn't concentrating on the smell, he would not need to make a bracha. (There is a similar M.Y. question about needing to make a bracha when entering a coffee shop.)
However, if one intentionally smells a bar of soap to enjoy its fragrance, what bracha should he make? Body soap has a combination of some natural products - sometimes aloe (a "fruit" plant - normally would have the bracha for smelling fruits); could be honey, might be oatmeal, wheat germ, and mostly it has chemical fragrances (is there any bracha ever made on synthetic fragrances?)
In short, what bracha should you make on bar soap?