The two main materials you need to get started are the textbook, How to Design Programs and to accompany it the programming environment, DrScheme. Both are available for free on-line, so you can check out the TeachScheme! curriculum without any expenditure. Then you have PLT DrScheme: Programming Environment Manual and The Scheme Programming Language, a free online book on scheme. PLT Scheme is an umbrella name for a family of implementations of the Scheme programming language.