Encyclopedias are great for:
Scholarly Subject Encyclopedias
Oxford Art Online Excellent articles and images.
Medieval art: a topical dictionary Leslie Ross. Westport, Conn. : Greenwood Press, 1996.
Late antiquity: a guide to the postclassical world (Olin Library Reference DE5 .L29x 1999)
Women and Gender in Medieval Europe: An Encyclopedia (Olin Library Reference HQ1147.E85 W66 2006)
Women in the Middle Ages: an encyclopedia. (Olin Library Reference HQ1143 .W643 2004)
Oxford Bibliographies Online: Medieval Studies Offers peer-reviewed annotated bibliographies on European and Mediterranean civilization from the 4th to the 15th centuries.
Dictionary of the Middle Ages. (Olin Reference D 114 D55+; also Uris Reference)
Medieval Italy: An Encyclopedia. (Olin Library Reference DG443 .M43x 2004)
Chronologies, Histories, and Atlases
Chronology of the Medieval World 800 to 1491. 1973.(Olin Reference D118 .S88 1973) This chronology focuses on western Europe, but an attempt has been made to show contemporary developments in other continents as well.
Atlas of Medieval Europe. 1997. (Uris Reference G1791 .M2x 1997)