JAVASCRIPTS:

// We add the "equalize" and "setRandom" methods to Elements
Elements.implement({

 equalize: function(property){
 var sum = 0, i, len;
 len = i = this.length;
 while (i--) sum += this[i].getDimensions()[property];
 var average = Math.round(sum / len);
 i = len;
 while (i--) this.tween(property, average);
 return this;
 },

 setRandom: function(property, min, max){
 var i = this.length, value;
 while (i--){
 value = Math.round(min + (max - min) * Math.random());
 this[i].tween(property, value);
 }
 return this;
 }

});

window.addEvent('domready', function(){

 var els = $$('div.element'), i = false;

 $('link').addEvent('click', function(event){
 event.stop();

 i = !i

 if (i) els.equalize('height');
 else els.setRandom('height', 30, 150);
 });
});

HTML:

<p><a id="link" href="#">Execute Example</a></p>

<div id="elements">
 <div class="element"></div>
 <div class="element"></div>
 <div class="element otherElement"></div>
 <div class="element otherElement"></div>
</div>

<h3>Code:</h3>
<pre>Elements.implement({

 equalize: function(property){
 var sum = 0, i, len;
 len = i = this.length;
 while (i--) sum += this[i].getDimensions()[property];
 var average = Math.round(sum / len);
 i = len;
 while (i--) this.tween(property, average);
 return this;
 },

 setRandom: function(property, min, max){
 var i = this.length, value;
 while (i--){
 value = Math.round(min + (max - min) * Math.random());
 this[i].tween(property, value);
 }
 return this;
 }

});</pre>

<h3>Usage:</h3>
<pre>myElements.equalize(property);
myElements.setRandom(property, min, max);</pre>

CSS:

#elements {
 overflow: hidden;
}

div.element {
 width: 100px;
 height: 50px;
 border: 1px solid black;
 background-color: #f9f9f9;
 float: left;
 margin: 5px;
}

div.otherElement {
 height: 20px;
}

pre {
 padding: 5px 7px;
 margin: 5px 0;
 background: #f5f5f5;
 border: 1px solid #ddd;
 color: #333;
 overflow: auto;
 font-size: 12px;
}