Encyclopedias are great for:
The Classics division has a number of useful full text titles:
New Pauly Online An aid for the study of Greek and Roman culture and its multifaceted presence in all periods of European and, since the Early Modern period, world history. Entries offer easy, direct access to basic information - names, places, dates, objects - from all areas of Greek and Roman culture as well as their predecessors, neighbours and heirs.
Oxford Art Online provides web access to the entire text of The Dictionary of Art, ed. Jane Turner (1996, 34 vols.) and The Oxford Companion to Western Art, ed. Hugh Brigstocke (2001). Articles, and over 1,500 thumbnail art images and line drawings, extensive image links, and sophisticated search and navigation tools.
The Oxford Companion to Classical Civilization. 1998. (Olin Reference DE5.O92x 1998+). A shortened version of The Oxford Classical Dictionary.
Ancient Writers Greece and Rome. 1982 (Olin Reference PA 3002.A54)
Grant, Michael, and Rachel Kitzinger. Civilization of the Ancient Mediterranean: Greece and Rome. 3 vols. New York: Scribners, 1988. (Olin Reference DE 59 C58 1988)
Sienkewicz, Thomas J. Encyclopedia of the Ancient World. 3 vols. Pasadena, CA: Salem Press, 2002. (Olin Reference CB311 .E54x 2002)
Encyclopedia of Greece and the Hellenic Tradition. 2000. (Olin Reference DF757.E53x 2000)
Brill's New Pauly Supplement vol 4. The Reception of Myth and Mythology
Encyclopedia of Greco-Roman Mythology. 1998. (Olin Reference BL 715 D56x 1998)
Early Greek Myth: A guide to Literary and Artistic Sources. 1993. (Olin Reference BL782.G21)
Encyclopedia of Ancient Dieties. 2000. (Olin Reference BL473 .C68 2000 +)
The Encyclopedia of Religion. 1987. (Olin Reference BL 31 E55+)
The Dictionary of Classical Mythology. 1986. (Olin Reference BL 715 .G86 1986)
Gods and heroes : a quick guide to the occupations, associations and experiences of the Greek and Roman gods and heroes. 1977. (Olin Reference BL715 .H29)
Funk and Wagnall's Standard Dictionary of Folklore, Mythology, and Legend. 1972. (Olin Reference GR 35 F98 1984)