The BBC website has a lot of resources buried in it. Here’s a neat one–a project on the beauty of maps with a very zoomable image of the mappa mundi from fol. 9 of the Map Psalter. This’ll be great for teaching. Here’s the page on the manuscript (Add. 28681) from the BL.
I’m listing some good web resources for teaching the middle ages under the “Nicely Done” category on the right–please add a comment if you know of any.