Here’s a wonderful video showing St. Vigor of Bayeux and his dragon. The music is the melody of a “cantique” sung for his feast day. The guy who runs the St. Vigor homepage made it, showing all the church art of the saint that he’s been able to find. (The ones with dragons in them, anyway.)
St. Vigor lived in the sixth century. He and his sidekick, Theudemir, did a bunch of evangelizing of Christians and pagans in Normandy. They were dealing with all sorts of people (Gauls, Franks, Norse, Bretons), and even ran into some kind of operational pagan Celtic temple (dedicated to Belenos, we are told).
Normandy is full of legends of dragon-slaying and dragon-drowning saints, but St. Vigor took a slightly different approach. When he had made the Sign of the Cross and made the dragon unable to resist him, and he had leashed the dragon with his stole in the best approved French style (making it “like a tame sheep”), he handed the dragon’s leash to Theudemir, with instructions to take it to the seashore, so that it would have no more power on the land.
Anyway, the taming of the Dragon of Cerisy Forest was legendarily the reason that Volusianus, a local nobleman, gave the land to St. Vigor to start the monastery of Cerisy. It shows up in the “Vita Sancti Vigoris,” which is apparently a pretty late life (10th c. is the current best guess).
The saint came to prominence again after the Viking invasions, when a cleric named Avitianus brought his relics from Bayeux to the monastery of Saint-Riquier. After various miracles happened, the Saint-Riquier monks started asking around for information, and got a copy of the Vita from the monks at Saint-Ouen. There are a couple of churches dedicated to him in England also, apparently because people moved to England from St. Vigor’s area of Normandy.
I’ve also run into a lot of interesting material at the Dragonlore site. The Journal of the College of Dracology folks have done a fair amount of solid heraldry and other research, in the Notes and Queries style.
They unearthed the point that even in the West, most dragons were seen as either “giant serpents” or “giant serpents with wings” until quite late in the day. The continuing use in battle of noisemaker-mouthed windsock dragon banners (the “draco” of Sarmatian and late Roman cavalry) helped this. Then the popularity of griffins seems to have influenced people to draw dragons with four legs and wings at that point. And yes, it does seem like most of the non-windsock “dragons” in the Bayeux Tapestry are really griffins or basilisks of some sort, because they look very birdy in front.
UPDATE: St. Carantoc also released a dragon into the sea, while St. Samson released one into a river. Apparently legend had a medieval English parish priest ordering a dragon to stay in the sea for a thousand years, which of course begs the question of what happens when he comes out. (Study hard, English seminarians!)