jQuery Templater, when you don't need a whole engine.

Templater.js

/**
 * Templater instance, pass in the selector for your template. And
 * a key'd object with your data. Use "{{ key }}" in your template
 * to replace values from this array.
 */
function Templater(template, data) {
    this.template = template;
    this.html = $(template).html();
    this.data = data;
    
    this.process(this.data);
}

/**
 * Process the template with some data, will be
 * called on construction of Templater by default.
 */
Templater.prototype.process = function(data) {    
    for (var index in data) {
        this.html = this.html.replace(new RegExp('{{ ' + index + ' }}', 'g'), data[index]);
    } 
}

// Example template:
// <script type="text/template" id="template">
//     <h1>{{ title }}</h1>
// </script>

// Example code for above template:

var templater = new Templater('#template', {title: 'This is my title'});

$('body').append(templater.html);