Pug!

Handlebars is a JavaScript template library that is, more or less, based on mustache . Handlebars adds user defined block expressions and helpers to the standard Mustache template syntax.

Underscore is a utility-belt library for JavaScript that provides a lot of the functional programming support that you would expect in Prototype.js (or Ruby), but without extending any of the built-in JavaScript objects. It's the tie to go along with jQuery's tux, and Backbone.js's suspenders.

Haml (HTML Abstraction Markup Language) is a lightweight markup language that is used to describe the XHTML of any web document without the use of traditional inline coding. It’s designed to address many of the flaws in traditional templating engines, as well as making markup as elegant as it can be. Haml functions as a replacement for inline page templating systems such as PHP, RHTML, and ASP. However, Haml avoids the need for explicitly coding XHTML into the template, because it is itself a description of the XHTML, with some code to generate dynamic content.Haml's equivalent for CSS is Sass. »

Mustache is a simple web template system with implementations available for ActionScript, C++, Clojure, CoffeeScript, ColdFusion, D, Erlang, Fantom, Go, Java, JavaScript, Lua, .NET, Objective-C, Pharo, Perl, PHP, Python, Ruby, Scala and XQuery.

Slm is a template language for js. Port of Slim but slimmer :)