War Time Military Maps

I attended a talk at my local library the other month and the subject was georeferencing old maps onto new maps. One useful piece of information given was a link to the National Library of Scotland web site that may be useful to Lost Cousins members who are trying to find where various battle fields of WW1 & WW2 are today.
Here's the link.

If you follow the links on that page to say, "Maps of Belgium/France", and select the "As zoomable overlays of each map on a modern Google or Bing map" option and then enter a place in the "Find a place" box on the left hand side, you can use the "Change transparency of overlay" slider in the bottom left corner to merge the old map onto a new map.

You can also use this site to similarly overlay non-military old maps of the UK onto modern maps.