On a second take, I'd share my experiences, and update Prestaul's answer.
In most cases, you don't just want to click on an element to induce the 'onclick' event, but you would like to use the click info for something (eg.: move a slider there, or put a popup at that exact place).
I'm mostly using vanilla js, but it blends well with $.
function simulateClick(x, y) {
var clickEvent= document.createEvent('MouseEvents');
clickEvent.initMouseEvent(
'click', true, true, window, 0,
0, 0, x, y, false, false,
false, false, 0, null
);
document.elementFromPoint(x, y).dispatchEvent(clickEvent);
}
Basically this will pass down the correct pageX / pageY through the event, for further use.
I have updated the fiddle as well, to show a use of these coords:
http://jsfiddle.net/V4CdC/