Essentially a two-image slideshow, where the images "reveal" each other through a film-like fade/wipe effect. Utilizes CSS3 image masks made from CSS3 gradients.
Multiple levels of images are used here to create a "door" link which slides up to reveal another image beneath. CSS3 transitions are used if available, otherwise falls back to jQuery JavaScript.
Using a combination of fixed positioning, relative positioning, and transparent /examples/images you can create a "secret message", which will only reveal itself if you scroll down and line up the letters. PSD included in the example which shows simple masking technique.
Probably overkill for most sitemaps, but this is a neat proof of concept that fades different "layers" of the sitemap to different colors as they are rolled over with the mouse.
Thanks to some CSS positioning tricks, we can actually have two different page elements in two different areas of the page use the same anchor link and react to the same hover event. Pretty cool effect that uses nothing but pure CSS and degrades very well.
Use color saturation with HSLa and arrow shapes built with psuedo-element CSS triangles to represent hierarchy with this breadcrumb navigation technique.
Parallax is very cool three-dimensional effect. "Closer" stars will appear to move faster while more "distant" stars move slower. This is achieved with transparent background /examples/images and percentage positioning. Downloads include Photoshop (.psd) file.
Using a small bit of javascript, you can create buttons which can switch between alternate stylesheets you have declared in your head section. You could do something as subtle and useful as bumping up the font-size, or do full-blown changes in layout and style. Careful though, rules from the original stylesheet will still apply, so if you don't implicitly re-declare every selector and attribute, you can get some holdouts.