As someone who grew up in a small(ish) town, I've long been fascinated by the thick web of networks in slightly-populated places. I think it's partly what drew me to early modern history--the realization that, with the exception of London, every city in sixteenth century England was smaller than my hometown. The inevitable connections of such limited social geographies has inspired a significant portion of my academic work. (Thomas Wolfe, it seems, was wrong.)
I digress. Networks lead to geographies, and geographies lead to maps. I've been playing around recently with self-created maps to illustrate my work and to create new analytic frameworks for my findings. The difficulty, of course, begins with the Victorians. The Local Governments Act of 1888 redrew county borders along post-Industrial lines, and later reforms in the 1960s, 70s, and 90s further obscured the historical boundaries of England. Good for local governmental reforms; bad for historians.
Most GIS data sets reflect post-Victorian borders rather than the administrative boundaries of early modern England--and as such, creating accurate maps can be difficult. Take, for instance, this map created by using the open-source data set from Natural Earth.
Natural Earth is fantastic, and I highly recommend looking through their data sets for any modern projects, geographical boundaries, etc. However, for the early modern historian, maps created from these boundaries aren't particularly useful.
Enter the Historic Counties Trust, a "Registered Charity which aims to promote public awareness of the history, geography, natural history, architecture and traditions of the historic counties of the UK." The Trust offers full GIS data sets for the pre-1888 county boundaries, open-source and freely available for both personal and commerical use. The much-simplified pre-Victorian borders are clearly articulated on a beautifully accurate map.
I'm still playing with the data sets from the HCT (no idea if that's what they call themselves, but I've always loved an acronym) in my mapping program, but thus far they've been hugely useful for imagining administrative and institutional boundaries. If only someone made an post-Reformation ecclesiastical boundary data set!