I think that the Scriptures paint a picture where man, while significantly constrained in respect to determining his destiny, indeed has some free choices. I am inclined to believe that neither of the following positions is correct:
1. Man's destiny is fully and completely prescribed (ordained in advance) by God.
2. Man has full control over his own actions (except of course, where other humans and / or the laws of nature interfere - one cannot control against being shot or struck by lightning, for example).
In defence of the notion that man's destiny is largely prescribed by God, we have texts like Psalm 139:6:
your eyes saw my unformed body.
All the days ordained for me
were written in your book
before one of them came to be.
In defence of the notion that man has some degree of freedom to establish his destiny, we have texts like Joshua 24:15 (as well as the text that "Stove" provided in this very thread):
But if serving the LORD seems undesirable to you, then choose for yourselves this day whom you will serve, whether the gods your forefathers served beyond the River, or the gods of the Amorites, in whose land you are living. But as for me and my household, we will serve the LORD.
Now some Calvinists have argued that Scriptural references to matters of "choice" to follow God are to be read with an understanding that God needs to provide man with an "ability to choose" - that man needs to be transformed by God in order to render him even capable of making the choice to follow God. Man in his natural state is incapable of making a choice for God.
In my experience, the texts used to support this idea are not conclusive - they allow for such an interpretation, but not to the exclusion of a more "Arminian" reading. It appears that, at some point, the Calvinist, or the hardcore Arminian for that matter, simply brings external pre-dispositions to bear and resolves these ambiguous verses in a manner that accords with what they are inclined to believe.
So for example, a text that states that man's days are ordained is interpreted to the effect that all man's choices and actions are ordained. This interpretation is indeed a possible one. But man's days can be ordained without needing to believe this - although the ordaining of the number of days Fred will live is indeed a severe constraint, it simply does not justify the conclusion that all of Fred's thoughts, actions, etc are similarly pre-ordained.
On the other hand, the Scriptures do make some rather powerful claims about the "fine-grained" control that God does exert (e.g. ordaining the number of days). This certainly imposes a number of secondary constraints on man's freedom to choose his own destiny.
In the end, I think that the Scriptures paint a picture that demands that we stretch our imaginations and not give in to overly simplistic interpretations of the degree of control we have over our destiny. I think that the Scriptures teach that we have some control, but probably a lot less than we would naturally think that we have.