[jQuery] Select links that end in .png, .jpg or .gif

Hello,
I use a light-box plugin on my website, http://www.FreeSoftwareWorkshop.com
and I need to select the links that end in .png, .jpg or .gif.
This is how I use the selector (it works only for .png):
$(function(){
$(".post a[href$=.png]").lightBox({
});
});
How can modify the above in order to select all the links that point
to images (png,jpg,gif)?
Thank you,
Nicholas