Applying easing to setTimeout delays, within a loop

This sounds like a job for Robert Penner's easing equations! You can download the original ActionScript 2.0 versions here (just remove the strong-typing on the parameters to port to JavaScript) and there's a good explanation of the parameters here.

Something like the following will do what you want (fiddle):

var time = 0;
var diff = 30;

var minTime = 0;
var maxTime = 1000;

// http://upshots.org/actionscript/jsas-understanding-easing
/*
    @t is the current time (or position) of the tween. This can be seconds or frames, steps, seconds, ms, whatever – as long as the unit is the same as is used for the total time [3].
    @b is the beginning value of the property.
    @c is the change between the beginning and destination value of the property.
    @d is the total time of the tween.
*/
function easeInOutQuad(t, b, c, d) {
  if ((t /= d / 2) < 1) return c / 2 * t * t + b;
  return -c / 2 * ((--t) * (t - 2) - 1) + b;
}

function easeOutQuad(t, b, c, d) {
  return -c * (t /= d) * (t - 2) + b;
}

function easeInQuad(t, b, c, d) {
  return c * (t /= d) * t + b;
}

for (var i = 0, len = diff; i <= len; i++) {
  (function(s) {
    setTimeout(function() {
      //self.turnPages(s);                           
      console.log("Page " + s + " turned");
    }, time);
  })(i);

  time = easeInOutQuad(i, minTime, maxTime, diff);
  console.log(time);
}