A very large site all dedicated to helping you learn about medieval paleography from England. Tons to see and do.

"Palaeography is the study of old handwriting. This web tutorial will help you learn to read the handwriting found in documents written in English between 1500 and 1800." While this is not strictly medieval good on-line paleography tutorials are hard to find. I think this is really work a visit and is an excellent way for learning about the process of decyphering handwriting.