The road to becoming a BCBA can be a really tough road. There is schooling, supervision, and other hurdles. However, it is worth it and I am pleasantly surprised about some things I have learned becoming a BCBA.
Applied Behavior Analysis: ABA info to help your child with autism - ABA Quizzes - Verbal Operant Quiz - Stimulus Prompts and Response Prompts Quiz - Good study material for the BCBA exam. A lot of great ABA info diagrams here as well.
Study Stack is an excellent site for creating flash cards. Also, a user can search through pre-made flashcards to find what's best for them. Another great feature are the educational games a user can play to help them study. There is a nice mobile app which works nice too for the users who prefer using mobile devices. tech tidbits