If you are looking for nice tooltip libraries, I recommend trying qTip2. It’s a jquery plugin. And it’s got most of the pop-up tooltip features you can imagine.

I personally like this feature, that you can assign different behaviors (by different actions) to the same element. See below:

// Create our first tooltip
$('.selector').qtip({
   content: 'Mouse entered',
   show: {
       event: 'mouseenter',
       solo: true // Only show one tooltip at a time
   }
})
 
// Remove the previous tooltips data
.removeData('qtip')
 
// Create our second tooltip
.qtip({
   content: 'Click',
   show: {
       event: 'click',
       solo: true // Only show one tooltip at a time
   }
});

With the above code, you can have a specified mouseover preview tooltip, and a detailed view upon a mouse click. Very handy!

Check out their demo page for all the cool features!