Result

jQuery

$('.email').each(function(i) {
    var mail = $(this).html();
    //置換文字の指定
    mail = mail.replace(" [at] ", "@");
    mail = mail.replace(" [dot] ", ".");
    //mailtoリンクに含める
    $(this).html(mail).replaceWith("<a href=\"mailto:" + $(this).text() + "\">" + $(this).text() + "</a>");
});​

html

Email : <em class="email">foo [at] example [dot] com</em>

via

Use JavaScript To Protect Your Email Address