Edit in JSFiddle

$.fn.blink = function() {
    setInterval($.proxy(function() {
        this.toggleClass('invisible');
    }, this), 500);
};

$.fn.blinkClosure = function() {
    var jQueryMonad = this, toggleClass = this.toggleClass;
    setInterval(function() {
        toggleClass.apply(jQueryMonad, ['invisible']);
    }, 500);
};

$('a').click(function(){
    $(this).blink();
});