A.R.Test
IXL
Learn Zillion
Lexia Core 5
MangaHigh
MobyMax
Reading Plus
Starfall
Study Island
TenMarks

ELA
A.R. Book Finder
Check if your book has an A.R. test
ISFE ELA
English and Language Arts Topics
Prep Dog
Free practice quizzes 
Scholastic
Reading games and writing tips

Math
AAA Math
Interactive math lessons for grades K-8
Coolmath
Math games, lessons, puzzles, brain teasers and much more for all ages
Interactive
Dedicated to the advancement of science and math education for middle school grades
ISFE Math
Math Topics
Prep Dog
Free practice quizzes 

Miscellaneous
ABCYa.com
Educational games for kids.
Enchanted Learning
Educational websites and games designed to stimulate creativity, learning, and imagination
ISFE Science
Science Topics
ISFE Social Studies
Social Studies Topics
ISFE Typing
Practice your typing skills.
National Gallery of Art
NGA Kids Art Zone
National Spelling Bee
Official website for spelling bee information
Picasso Head
Create your own masterpiece

Reference 
Fact Monster
Information and reference source
Merriam-Webster
Online dictionary and thesaurus
Noodle Tools
Create citations
Online Newspapers
Thousands of world newspapers at your fingertips
Refdesk.com
A one-stop site for all things Internet including news, weather, sports, encyclopedia
Rhyme Zone
Find a dictionary, thesaurus, antonyms & synonyms and much more
Thesaurus.com
What's another word for ______?