http://www.mythweb.com/ This site is devoted to the heroes, gods and monsters of Greek mythology.
http://www.pantheon.org/main/search.html Tons of info.
http://www.theoi.com/ More information than you can shake a stick at.
http://www.greekmythology.com/ Info you can use.
http://homepage.mac.com/cparada/GML/ Searchable by character, topic, place, or image
http://www.historylink102.com/greece2/index.htm Even more information for you
http://www.wingedsandals.com/ super cute, animated database; includes games, arts and crafts, historical information, myths, quizzes, etc.