While in the car today, I listened to a debate between a Reformed pastor and an open theist. You can download the debate here.
Open theism, as represented by this debater (a pastor by the name of Bob Enyart), is way off. It's the idea that God does not exhaustively know the future or decree what will take place in the future. Instead, God chose to create a universe in which the future is not entirely knowable, even for Himself. Thus man is able to shape future events that God must react to. This puts man in the driver's seat and strips God of His beautiful attributes of sovereignty and foreknowledge.
Enyart basically ended up saying that God is not omnipotent, omniscient, omnipresent, or immutable. God's "more important" attributes are love, goodness, and being personal and relational. True, He is all those things, but nowhere does the Bible justify categorizing God's attributes as more important and less important. Yet that's what this guy believes. He said that we in the Reformed camp are captive to Greek philosophy instead of the Bible, yet he ignored all the Scriptures that teach God's all-knowing, all-powerful, sovereign character.
Interesting stuff worth listening to.