http://cooltoolsforschools.wikispaces.com/ - An incredibly comprehensive list of tools for education.

 

http://www.softschools.com/ - A free site that has games, lesson plans, and worksheets for teachers and students.

 

Study Island - A site that allows students to take quizzes based off state test questions.  Teachers are able to give assignments and get grade reports. 

 

http://www.abcya.com/ -

 

http://sheppardsoftware.com/ - Educational games, quizzes, and lessons, activities and articles grouped by subject and grade level.

 

http://www.maths-games.org/ - A collection of online math games.