As to the impact of foreknowledge on the free will vs. absolute predestination issue, here is the sum of it.
According to Calvinism, God says what he will do, then does it. He says, "This man will be saved" from the reaches of eternity, and that man is "elected," that is, chosen, to be one of the heirs of salvation. This is done with no condition in God's mind, but is simply done because God says so.
According to Arminianism, God bases his predestination, his election, upon a set condition, in essence saying, "I will elect as my own all those men who make positive response to my drawing, and will give them faith." Thus, election in the Arminian scheme is defined as God foreseeing who will meet his condition, and based upon the meeting of that condition, electing them. (That is the short of it, although God is definitely shortchanged in his involvement in this description--Arminianism says that God has an active role in salvation, but does not say that it is God alone; it could be said, All God, and All us, but not God alone.)
In response to this, Calvinism states that "foreknowledge," like the author of this piece here says, is almost equivalent to predestination--God pre-plans that this is so, in essence, therefore it is so. Truthfully, I'm more inclined to see this as a reworking of the definition of foreknowledge than a factual definition--then again, I also realize that I am biased, and that Calvinists believe that I, as an Arminian, have reworked the concept of predestination.