Simple jQuery code snippet to add an event to all links with class .popup to open in a popup window instead of the current page or new tab/window. Specify the heights and widths as you please.

jQuery(document).ready(function ($) {
    jQuery('a.popup').live('click', function () {
        newwindow = window.open($(this).attr('href'), '', 'height=200,width=150');
        if (window.focus) {
            newwindow.focus();
        }
        return false;
    });
});