airslash.net

Found this on Reddit comments while reading about Facebook implementing the code on their pages. (heh)

Here’s how to do this.

konami = function()
{
	alert('konami');
};
var r = [];
document.onkeydown = function(event)
{
	r.push(event.keyCode);
	if (r.length > 11)
		r.shift();
	if (r.join('') == '3838404037393739666513')
		konami();
};

Demo here.

Konamicodesites.com has a list of the websites implementing the Konami codes.