Baking soda is just sodium bicarbonate, whereas baking powder is a mixture of sodium bicarbonate and, for example, tartaric acid used as a raising agent in baking. (Well...that's what Chanbers Dictionary says!)
NO! And take it from someone who found out the hard way... :) The components are as Quizmonster stated; baking soda should always be used sparingly in recipes and is not interchangable with baking powder.