I have discovered a site which has some useful and interesting maps. It is at http://www-sci.uni-klu.ac.at/archeo/index.htm
I could only get the information text in German but there is a map of Noricum I would have killed for when I was playing the Governor of Noricum (the coloured bits show the areas of the province linked with each Colonia). There is also a map showing the Empire during the reign of Diocletion with all the Dioceses marked - useful for those of us for whom a picture is worth a thousand words!

Cornelia Tertius