Encyclopedia Mythica: http://www.pantheon.org/

The Myth Encyclopedia: http://www.mythencyclopedia.com/

MythWeb: http://www.mythweb.com/ (Greek & Roman)

Myth*ing Links: http://www.mythinglinks.org/

Perseus Digital Library: http://www.perseus.tufts.edu/hopper/ Lots of classical texts in translation

Theoi Greek Mythology: http://www.theoi.com/

Women in Greek Myths: http://www.paleothea.com/

Moya K. Mason, "Annotated Bibliography of Women in Classical Mythology:" http://www.moyak.com/papers/women-classical-mythology.html

Tracy Osborn, "Teacher Oz's Kingdom of  History--Mythology, Legend, Folklore, and Ghosts:" http://www.teacheroz.com/myth-legend.htm (A 9th-grade world cultures teacher in TX with more energy than I can imagine...)

Digital Librarian: Mythology: http://www.digital-librarian.com/mythology.html A gazillion links to online texts

11th Encyclopedia Brittanica (the encyclopedia for literary stuff): http://www.1911encyclopedia.org/Main_Page

New Catholic Encyclopedia: http://www.newadvent.org/cathen/

Folkore and Mythology: Electronic Texts: http://www.pitt.edu/~dash/folktexts.html

Mythography: Greek, Roman and Celtic mythology and art http://www.loggia.com/myth/content.html

World Myths and Legend in Art (Minneapolis Institute of Art): http://www.artsmia.org/world-myths/

Comparative Mythology Working Group (apparently a Berkeley class in 2002): http://orias.berkeley.edu/2003/myth/mythlinks.html

National Air & Space Museum, Mythology of Star Wars: http://web.archive.org/web/19980523162727/http://www.nasm.edu/StarWars/guide.htm

Broken Links: You can always try to find archived copies of broken links by using the Wayback Machine at www.archive.org.