Here are some links that we at NMSC have found to be helpful.

Mathematics
    21st Century Problem Solving
    Geometry Center
    Math Forum
    World of Escher
    The Explorer
    Math Problems of the Week
    MathMagic!

Science
   Benchmarks for Science Literacy
    Dinosaur Exhibit
    The Electronic Zoo
    Franklin Institute Science Museum
    U.S. Geological Survey
    National Geographic Online
    Chemistry
    Newton's Apple
    Bill Nye the Science Guy
Need Help with Science Projects?  Try:
    Cyberspace middle school
    Science Snackbook
    Science Fairs
    Scholastic Network
   

Technology
   Michigan Electronic Library
    Teaching with Electronic Technology

Integrated
    Guide to Math and Science Reform
    Eisenhower National Clearinghouse
    The Explorer
    Math and Science Education Resources

Professional Development
    NCREL Pathways to School Improvement
    NASA Spacelink for educators
    Teacher Talk
    Green Teacher
    Teachers.net


Links of Interest to Teachers compiled by Carl Wosniak