These links are divided by age simply to aid in finding what you can use more quickly, based on known curriculum units. That doesn't mean you can't use them all!

High School

Read full text articles from magazines and newspapers; find current reference sources; use advanced search functions
Great research material for history, especially World Wars 1 and 2.
Courtesy of MelCat, this index of magazine articles is created by EBSCO and allows you to search by topic over 300 magazines from 1983 to the present.
Open access scientific and scholarly journals
Hathi Trust is a partnership of academic & research institutions, offering a collection of millions of titles digitized from libraries around the world.
The Purdue University Online Writing Lab (OWL) has great info on writing, research and citation, APA and MLA formatting, and ELL.
Paper Rater is a place to check your work for plagiarism as well as general proofreading.
Generate your Works Cited page. Includes APA format for free.

All Grade Levels

ReadWriteThink's website has links for learning how to research a topic, organize your notes, and create a good report or essay, as well as other prose, poetry, and other essentials--even for the youngest learners.

Middle School

Ducksters History for Kids site has information you can use about a whole lot of historical events and people.
Not only history, this site also has geography, religions, holidays, wars and more.

Elementary School

This is a great website to go to with your questions about things like dinosaurs, amazing things God created, and science stuff.

Endangered Animals
Inventors