Drag the boxes, stretch the lines
Update: A nice mention and ensuing discussion of this has appeared with this article at Lambda the Ultimate. I've killed trackback here due to spam, so I'm tossing this in manually.
It's likely to only work on Firefox and Safari, but check it out and drag the boxes around:
View the source, steal anything worth theft, make fun of what's bad. Oh yeah, and don't mind the ugly background images too much: They were just some random textures I picked out of The Gimp in order to see just how well the transparency on distorted PNGs worked.