I'm working on a pet project that places a heavy emphasis on English geography circa 1200, and I'm in desperate need of a better map to work from. The more detail the better, especially regarding county lines, important towns, castles, trade routes, geographical features, etc. The map doesn't have to be online of course, if its in a book and worth it I'm happy to buy it. Local county maps would help as well. Thanks!
The Digital Atlas of Roman and Medieval Civilization has some of the things you need. I would also recommend looking at:
Bengtson, Hermann, and Vladimir Milojčić, eds. Grosser historischer Weltatlas: Erläuterungen. 4 vols. München: Bayerischer Schulbuch-Verlag, 1996.
Jedin, Hubert, Kenneth Scott Latourette, Hans Quast, and Jochen Martin, eds. Atlas zur Kirchengeschichte: die christlichen Kirchen in Geschichte und Gegenwart. Freiburg: Herder, 1970.
Both are in German, but it's maps so it's nothing you can't handle, I'm sure.
The Braun/Hogenberg: Cities of the World (Civitates Orbis Terrarum) is an awesome, full-color atlas full of old town maps. They're not all England-based, but it's still fantastic. I've been drooling over it for 6 months though, so I might be biased.