There are four buttons on this example, each of which has three states. That would normally be 12 images (thus 12 server requests), but thanks to the CSS sprites technique it is only one. The technique is demonstrated practically in the form of an accordion widget.
This is an alteration based on the jQuery "Coda Slider" plugin. Each "slide" can be any kind of html content whatsoever, or be a full-size image with an overlay. Each slide also has a unique thumbnail which can be clicked to go to the corresponding slide, with an arrow above it to indicate the active panel. And... its auto-playing!
Many of the webs "social" sites offer up API's to get data out of them for use on your own sites. Sites like Flickr, Twitter, and ScrnShots offer up these API's in JSON format which makes it really easy for us to grab and display this information on any ol' static page. This example uses jQuery to grab and display the info. Should be fairly easy to alter to pull your own stuff.
A line of cropped photo thumbnails on a string. Clicking the "More Info" button expands the photograph to full size and reveals additional information about the photo. Photos are loaded on page load so there is no waiting after the click. Uses jQuery.