Does God have a Plan?

I am a planner. I like to know who's doing what and when, and how long it will take. In my younger days, I never needed to keep a calendar; I could simply remember what was happening and where I needed to be. After having children, however, all that has changed. I need a family calendar to remember what each member of the family has scheduled on a particular day. Now, don't get me wrong, I do like spontaneity, and I'm all for surprises. On a day to day basis, though, I pretty much like to know what's going on.
In spite of my planning, though, often it seems that the plan goes awry. For instance, every morning it is my goal to leave the house at 7:00. I get up in plenty of time to get myself and my son ready to leave by 7. But, every morning, something happens to set that plan off track -- Jonah doesn't want to get dressed, or I need to help Kayla with her hair, or I can't get into the bathroom to brush my teeth. You name it, it has happened. So, every morning, we leave the house at 7:20. Of course, usually it's not my fault that we are leaving late; it's because somebody else in the house put my plans off track :-)
I wonder sometimes if it is like this with us and God. Nearly every Christian I have ever met (and that's a lot!) has indicated that they believe, to some extent, that God has a plan for the world. If someone dies, it is "part of God's plan." If a natural disaster wipes out a city, it is because "God planned it that way." Just last night, I heard a complete stranger on her cell phone telling someone that they got a job promotion because it was in God's plan. All that being said, though, I wonder what people would say if I asked them to what extent God plans out everything that happens in this world, and to what extent they think human beings mess up God's plan.
You see, I think that in order to say that something is "part of God's plan," we presume to know what God's overall plan for the world is. In other words, by saying such a thing, we indicate that we know the mind of God. Even the Bible is not quite clear on the issue. Job 38-41 is a series of rhetorical questions that God asks Job to show that Job can never know what God knows. Adam and Eve got kicked out of the Garden of Eden for the desire to know what God knows. Ephesians 3:8-9, however, says that the church is responsible for making God's plan known to the world, yet it is not too difficult to see that "the church" does not quite agree on what God's plan is.
What do you think? Does God have a plan? If so, how can we discern the nature of the plan, or even the extent to which God plays a hand in executing the plan? Are we all just God's puppets, or do we have the ability to mess up God's plan? As we move into discussion about the book of Revelation, think about God's plan and the end of time. What do you think will happen?