I have been working on a side project at work and in my spare time digitising some old maps I had, you can read more on the back story to these maps here.
Basically leveraging the power of the Google Maps API and a little Ruby foo to generate the tile pyramid I have set up www.oldmapsofparis.com as an easy way to look at the various historic maps online. As I only had a few originals and these maps copyright has now expired, I was able to add to the project's collection by finding some other high quality maps on wiki commons.
There are currently 25 maps that date as far back as around 360ad. These were created in 1705 based on the historic records of the time but collectively they make an interesting way to view the evolution of a city.
You can download the full size map image from each page and I have also made the maps embeddable so that they can be included on blogs or even (if you happen to be based in an old street in paris) as an alternative to your location map.