Interested in learning more about medieval manuscripts? Here are some sites to check out.
The Free Library of Philadelphia has an online guide to manuscript basics. This includes information on the various types of manuscripts, how they were used, and how they were made. They have links to other resources about manuscripts and you can take an online tour of their manuscript collection. For more information please see https://libwww.freelibrary.org/medievalman/guide.cfm.
The J. Paul Getty Museum in Los Angeles has created a short video that guides the viewer through the making of a medieval manuscript. The video is available at https://www.youtube.com/watch?v=1aDHJu9J10o.
The British Library has one of the largest collections of medieval manuscripts available online. There is a search feature to look for a particular item, or you can tour all of the virtual exhibitions. http://www.bl.uk/catalogues/illuminatedmanuscripts/introduction.asp
If you would like to learn more in depth history on manuscripts, Harvard offers a series of free courses through edx.org on the history of the book. Some examples of these courses include The Book: Making and Meaning in the Medieval Manuscript and The Book: The Medieval Book of Hours: Art and Devotion in the Later Middle Ages. Courses are available through https://www.edx.org/.