Tutorial Automatically Discover Document Links And Apply Class
$('a[href]').each(function() {
if((C = $(this).attr('href').match(/[.](doc|xls|pdf)$/))) {
$(this).addClass(C[1]);
}
});
This will look through every a element on the page. If the href attribute of it has a .doc, .xls, or .pdf in it, it will apply the appropriate class name to it (e.g. class="doc")