Edit in JSFiddle

$( "a" ).attr( "href", "http://monoforms.com" );
 
$( "a" ).attr({
    title: "Agregar un atributo con jQuery!",
    href: "http://monoforms.com/Agregar%20un%20atributo%20con%20jQuery"
});

<div>
    <a href="#" target="_blank">Monoforms</a>
</div>