http://school.discoveryeducation.com/teachingtools/teachingtools.html
http://school.discoveryeducation.com/curriculumcenter/?pID=curriculum
Includes Puzzlemaker, Quiz-Center, Lesson Plan Organizer, Clip Art, Worksheet Generator.
http://school.discoveryeducation.com/students/?pID=learn
Social Studies, mostly middle school level.
http://school.discoveryeducation.com/schrockguide/?pID=kathy
Numerous links to websites on everything from builletin board ideas to rubrics to subject-specific links.
http://www.sdst.org/shs/library/tealinks.html
Joyce Valenza is the Library Media Specialist at Springfield High Schools in Erdenheim, PA. She is a pioneer of the "virtual library" and her site lists hundreds of resources for teachers.
http://www.free.ed.gov/index.cfm
US Government site that links to web resources and exhibitions.