Add comma to numbers every three digits

@Paul Creasey had the simplest solution as the regex, but here it is as a simple jQuery plugin:

$.fn.digits = function(){ 
    return this.each(function(){ 
        $(this).text( $(this).text().replace(/(\d)(?=(\d\d\d)+(?!\d))/g, "$1,") ); 
    })
}

You could then use it like this:

$("span.numbers").digits();