Handlebars!

Pug, formerly Jade, is a high performance template engine heavily influenced by Haml and implemented with JavaScript for Node.js and browsers.

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.

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.

A template plugin for jQuery. Allows templating without cluttering JavaScript code with markup. Simple, Concise yet powerful.

Interpose.js is a tiny, fast and flexible JavaScript templating engine that uses native JavaScript as its expression language, and configurable expression delimiters. Templates can come from any source, and are compiled into functions that can be applied to models numerous times, so templates do not need to be repeatedly parsed.

Javascript templating engine. It inherits its look from the ctemplate family of languages, and is designed to run asynchronously on both the server and the browser

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