$('a:not(.no-tracking)').each(function(){
    var link = this;
    if (link.hostname && link.hostname !== location.hostname){
        $(link).bind('click keypress', function(event){
            var code = event.charCode || event.keyCode;
            if (!code || (code && code == 13)){
                _gaq.push(['_trackEvent', 'Outbound Links', this.href, this.title]);
            };
        });
    };
});

Google Analytics: Tracking outbound links

jQuery