EDIT MAIN
Plus_blue

Academic Websites

Common Core Standards

Cybraryman.com This site has access to over 20,000 websites and is very thorough - it's an excellent resource for all grade levels. 

Khan Academy This site is best known for math but is also good for science and has added art history. It contains videos for all levels.

Math.com Get help with math at all levels even provides homework help

Great place to get Math homework help

Marcaria- Internet Resources on Citation

Powerschool for Parents

Powerschool for Teachers

Spellingcity.com Great site for spelling and vocabulary primarily for elementary

Studyladder.com A comprehensive site of all disciplines and levels

WolframAlpha.com This is a fact-finding site, probably best for junior high/high school