Jade is an elegant templating language focused on enabling quick HTML coding. No more XML situps and percent prefixes for tags. It is HTML templating how it should be.
Learn more at jade-lang.com or check out the tour. If you want to start experimenting in a sandbox environment, head over to the playground or check out the public API.
There is also a platform SDK to help quickly setup a Jade powered environment.
<!DOCTYPE html>
<html lang="en">
<head>
<title>Jade Rocks!</title>
<script>console.log("hi");
</script>
</head>
<body>
<p class="greeting">Hello, World!</p>
</body>
</html>
Check out Markup Hive, a complete development and hosting platform service that supports Jade as well as other popular web technologies such as CoffeeScript, Less, SCSS, and Markdown.