Mouse XY for Chrome
More About Mouse XY
This will give you the x and y coordinates of a point on your screen. Clicking once alerts the ordinates to your screen. If you want to continue collection of points, press Ok on the confirmation dialog and click again. When you are finished, click cancel on the confirmation dialog.
New Features: Collect A list of co-ordinates, opposed to just 1 set at a time like the previous version.