ZofZ. All the rest is crap.
Despite it is not an online viewer, I agree that it is quite nice. Unfortunately I have a mac. I have tried it through Parallel, but the supposedly intuitive interface is far from intuitive for me. I was not able to find how to zoom.
So I am still looking for a good online gerber file viewer, that would show, as in zofz, the full finished pcb, with the drilling.
Here is the view from ZofZ of my board. It is not with full resolution, as it is just a screen view.