Super simple jQuery slider
In this code, you set sDone = true in both branches of the if-else:


if (next.size()) {
    next.addClass("secondary");
    sDone = true;
} else {
    images.filter(":first").addClass("secondary");
    sDone = true;
}



So you could move that line outside of the if-else:

if (next.size()) {
    next.addClass("secondary");
} else {
    images.filter(":first").addClass("secondary");
}
sDone = true;




At the top you declared the current variable,
but then you don't use it. If you don't need it, then remove it.