From i.e. Magazine's August 2005 issue:

Science

Backyard Jungle
http://pbskids.org/backyardjungle
Explore this excellent tool for teaching students about the flora and fauna in local communities. Students and teachers can load photos, drawing and descriptions about their natural surroundings.
Secondary

ISAW - Interactive Science Activities on the Web
http://www.bridgewater.edu/departments/physics/ISAW
Try out the free activities about interactive visualizations of scientific concepts. While designed primarily for high school and college students, this website is a terrific resource for anyone interested in science.
Secondary

Neuroscience for Kids
http://faculty.washington.edu/chudler/neurok.html
Explore the nervous system in this detailed website that includes many activities, experiments, articles, research and other resources.
Elementary

EcoKids
http://www.ecokidsonline.com/pub/index.cfm
Learn about the environment through interactive, educational games and activities on this award-winning website that encourages learners to form opinions and get involved.
Elementary

Language Arts

Online Poetry Classroom
http://www.poets.org/page.php/prmID/6
Visit forums where teachers can share ideas, seek help from colleagues and explore curriculum units, lesson plans. biographies of hundreds of poets and nearly two thousand poems.
Elementary (second grade)

The Neverending Tale http://www.coder.com/creations/tale/
Check out this choose-your-own-path story site where readers can add to stories, which encourages independent learning of reading and writing.
Elementary/Secondary

Reading is Fundamental (RIF)
http://www.rif.org/educators/activities/online.mspx
Take your class on a reading adventure and access fun activities, lesson plans, articles and Web resources.
Secondary

Math

AAAmath.com http://www.aaamath.com/
Access hundreds of pages to enhance math skills with interactive practice for every kind of math problem. This is a great resource with basic teacher resources and challenging math games for students.
Elementary/Secondary

Aplusmath.com
http://www.aplusmath.com/
Check out this online resource designed to help students improve their math skills interactively with the use of flashcards, worksheets, puzzles and a game room.
Elementary

ArithmAttack
http://www.dep.anl.gov/aattack.htm
Download the free ArithmAttack program and test your math skills with these computer generated arithmetic problems.
Elementary/Secondary

CoolMath.com
http://www.coolmath.com/
Explore a world of math where difficult problems can be fun and discover hundreds of resources, exercises and an amusement park devoted exclusively to math.
Secondary

NCTM: Illuminations
http://www.illuminations.nctm.org/
Explore the future of math in schools with this website's extensive listing of lessons, standards, tools and Web resources compiled by the National Council of Teachers of Mathematics.
Elementary/Secondary

Mrs. Glossers's Math Goodies
http://www.mathgoodies.com/
Check out this free math help site featuring interactive lessons, puzzles, and worksheets. This site has provided free homework help since 1999 with over 400 activities for parents, students, and teachers.
Elementary/Secondary

Cross-Curricular

AOL@School
http://school.aol.com/
Explore this resource that provides educator reviewed classroom resources for K-12 students and teachers. You will quickly find activities, research materials, multimedia resources and lesson plans for math, science, language arts, social studies, and more.
Elementary/Secondary

edHelper.com
http://www.edhelper.com/
Check out this subscription service website that was created by teachers to offer educational resources, including worksheets, lesson activities, classroom helpers and monthly themes in math, science, language arts and social studies.
Elementary/Secondary