Geekfont
The Geekfont is a monospace font using pure CSS, no images. With stylesheets deactivated, you’ll see plain HTML text. The characterset is a bit limited (each sprite is just 6×3 squares), but the most important stuff is there. There are only 9 CSS classes but a lot of <span> tags wrapping the characters. Try it out and don’t forget to take a peek at the source code!