[Thanks to Colin Chater on Northumbria list for this].
The National Library of Scotland has scanned maps as high-resolution, colour, zoomable images. The maps date between 1560 and 1964 and relate primarily to Scotland, although they also have maps of areas beyond Scotland, including England and Great Britain, Ireland, Belgium, and Jamaica.
With this web link you can access and view all their maps. The easiest way of finding material relating to any particular location is to find by place. The boundaries and extents of all the map images are shown as clear coloured overlays that you can select and view. The screen images can then be saved as pdfs.
Web site address is: http://maps.nls.uk/