Phell,, I actually have been to Versailles 7 times now.. er,, a little obsession. Its always been crowded, but surprisingly( or perhaps not) the least crowded time I have been inside the palace was when my dd and slept in and didn;t get out there till after 1 in the afternoon.
I attribute the slight lull in crowding to the fact that most tour groups and buses seem to pull up in the morning . Plus of course all the other tourists who like to get there first thing.
Now, I don;t know if I would recommend going that late in the day,, we didn;t seem to have as much time as I would have liked to cover the whole grounds and out buildings,, but, it was definately less crazy inside.
I personally would go on friday, not sat or sun if you are trying to minimize the crowds for your visit, the weekends are always more crazy because of the fountain show in gardens( which, yes I know puts me in minority as I didn;t consider extra crowds worth the 1/2 hr fountain displays with the taped music)