Rachel Held Evans is interviewing Greg Boyd on Open Theism, and here’s his opening explanation, and there are questions and responses at her site:
To expound a bit on this definition, the open view of the future holds that God chose to create a cosmos that is populated with free agents – at least humans and angels (though some hold that there is a degree of freedom, however small, in all sentient beings). To have free will means that one has the ability to transition several possible courses of action into one actual course of action. This is precisely why Open Theists hold that the future is partly comprised of possibilities. While God can decide to pre-settle whatever aspects of the future he wishes, to the degree that he has given agents freedom, God has chosen to leave the future open, as a domain of possibilities, for agents to resolve with their free choices. This view obviously conflicts with the understanding of the future that has been espoused by classical theologians, for the traditional view is that God foreknows from all eternity the future exclusively as a domain of exhaustively definite facts.