Other lists of essential Jewish websites:
Gannopedia includes a marvelous filterable annotated bibliography of 254 essential Torah websites. (Gannopedia is run by a pluralistic Jewish high school in Boston.)
Another great meta-index of Torah and Jewish websites: Jewish Sources on the Net by Dr. Melech Tanen. <!-- It used to be hosted on the hashkafah.com forums -- http://www.hashkafah.com/index.php?s=&showtopic=12610&view=findpost&p=777526 -- but is now hosted on Google Docs. -->
Wikipedia also hosts an annotated bibliography of Torah e-text websites. It discusses hebrewbooks.org, Mechon Mamre, and about ten others.