Dunno if I've blogged this before, but it bears repeating.
How can God be sovereign, but humans still have free will?
Look at it this way. Conceptually, I could write a computer program that carries out an action on the basis of a random number. Then I could set the seed of the random number generator. Which means I can know (as the author of the program) exactly what random number will appear, and hence how that program is going to behave. But from the perspective of the program, it was coded to cover any random value that appears at that point. There is a difference between my knowledge (as programmer) and the program's "knowledge". The program is written in such a way that it is able to deal with any value that pops up, even though I know as the programmer what value it will get and hence how it behaves.
Now I believe that God is sovereign. From his perspective, he knows what I am going to do - indeed, he has ordained it. But as a human, I have absolutely no knowledge of what he has ordained - and I am acting as far as I can tell perfectly freely. Furthermore, I have the potential as a human being to act perfectly freely - I am not a robot constrained to behave in a particular way.
People argue that if I believe God is sovereign, then I weaken human freedom. But since my knowledge of the fact that God is sovereign tells me nothing about what God's plan is, nor does it constrain my behaviour in any way, I don't see that it is wrong to describe me as being free, and also responsible.
I can think of all sorts of illustrations that would relate to this. The disciples all knew that somebody was going to betray Jesus - but Judas still did it. The Bible said that the Servant would be cut off from the land of the living - and it still happened.
On a more domestic scale, I might forbid a small child to do something - in the fairly sure knowledge that they will not listen to my prohibition. I "sovereignly" know that the child will disobey my prohibition - but that makes the child no less responsible when he or she does what I have asked him or her not to do.
Update: I thought I'd posted something like this before. See here - a more substantial post.