An excerpt is below, but the full post is worth reading.
As of last week, the MLGB3's online database included over 6,000 records for books and manuscripts owned by medieval libraries. In order to look at them in aggregate I used the ever-helpful wget utility to pull down each record in order. I was left with a gigantic mess of html with the useful data hidden within it. After extensive cleanup and parsing of the data I was able to throw the location names of the original medieval libraries as well as current owners against David Zwiefelhofer's geocoding service (which I believe uses the Yahoo API) to get longitudes and latitudes. This didn't go entirely smoothly as the names of ruined monasteries tend not to register very well in geo databases. Fortunately, there are a wealth of wikipedia entries providing detailed long./lat. information on a wide range of English historical sites and I was able to fill in the blanks.
|Libraries in Medieval Great Britain (MLGB3)|
|Current Locations of Books from the MLGB3|
|Worldwide Current Location of Books in MLGB3|