Turning the Pages
Step into the British Library and turn the pages of two medieval manuscript's, the Sherborne Missal and Sultan Baybars' Qur'an. You can look at the documents page-by-page and zoom into sections of each page for a detailed look.
Source: British Library Intended Audience: General Reading Level: Middle School Teacher Section: No Searchable: No

Medieval Art
You'll find over 2,000 images of Medieval art at this site.
Source: Cleveland Museum of Art Intended Audience: General Reading Level: Middle School Teacher Section: No Searchable: Yes

Leaves of Gold
Learn about the Medieval art of illumination. You can browse through the pages of manuscripts, learn how manuscripts were made, and even design your own manuscript online!
Source: Philadelphia Museum of Art Intended Audience: General Reading Level: Middle School Teacher Section: Yes Searchable: No

Medieval Art
Take a virtual tour of some of the Met's collection of Medieval art.
Source: Metropolitan Museum of Art Intended Audience: General Reading Level: Middle School Teacher Section: No Searchable: No

The Cloisters
Take a virtual tour of some of the works housed in the Cloisters, the branch of the Metropolitan Museum devoted to the art and architecture of medieval Europe.
Source: Metropolitan Museum of Art Intended Audience: General Reading Level: Middle School Teacher Section: No Searchable: No

Medieval Art
You'll find images of early Christian and Byzantine, Romanesque, French Gothic, and Islamic art at this site intended to enhance undergraduate art history course work.
Source: Art Images for College Teaching Intended Audience: Students/Teachers Reading Level: Middle School Teacher Section: No Searchable: No

Italian Painting of the 13th-14th Centuries
Take an online tour of Medieval Byzantine and Italian paintings at this site from the National Gallery of Art.
Source: National Gallery of Art Intended Audience: General Reading Level: Middle School Teacher Section: No Searchable: No

The Glory of Byzantium
Learn about the history and art of the Byzantine Empire at this site from the Metropolitan Museum of Art.
Source: Metropolitan Museum of Art Intended Audience: General Reading Level: Middle School Teacher Section: Yes Searchable: No

Medieval Art Collection
This museum's site has examples of Byzantine, Ethiopian, French, Italian, Iranian, and Spanish Medieval art.
Source: Walters Museum Intended Audience: General Reading Level: Middle School Teacher Section: No Searchable: No