Intute Humanities Note: closed and not maintained as of July 2011.
A combination of the former Humbul Humanities Hub and Artifact sites. Most comprehensive!
IPL2 Arts & Humanities Reference
IPL2 Arts & Humanities Reference organizes site by discipline categories such as "History," "Literature," and "Philosophy". There are also links to other comprehensive humanities sites.
VoS Voice of the Shuttle
From University of California Santa Barbara, most comprehensive!