Click on the Load button, and the image will be displayed. You can put any image you like, as long as the address is valid.

This will display where your mouse-pointer is:

Any click on the image (that you have to load first), will be recorded in this textarea. By clicking reset you can empty the contents

These coordinates we can now put in an image-map such as this:

<img src="something.gif" usemap="#STH">
<map name="STH">
<area shape="poly" href="http://some.url" coords="-+ insert here +-">
</map>

In this case the clicks won't result in the actual coordinates in the image, for that the image should be in the top-left corner of the screen.
I could have compensated for that, but instead i decided to keep this script simple - as to avoid browser incompatibilities.
The Source-page contains a full working script, that will work immediately, without installation or having to alter values. Just download it, open it, load the image and click away!