GoogleLinkTracker.js

    var link = {
        href: "",
        _url: function() {
            var key = "/download.axd/";
            return this.href.substr(key.length);
        },
        extension: function() {
            return this._url().substr(33, 3);
        },
        filename: function() {
            return this._url().substr(this._url().search("/?d=") + 3);
        },
        path: function() {
            return this.filename() + "." + this.extension();
        }
    };

    $("a[href*=/download.axd/]").bind("click", function(e) {
        link.href = $(this).attr("href");
        _gaq.push(['_trackPageview', '/downloads/' + link.path()]);
    });