Newsela: https://newsela.com/
Readworks: https://www.readworks.org/
Flocabulary: https://www.flocabulary.com/
Grammaropolis: https://www.grammaropolis.com/
FreeRice: http://freerice.com/#/english-vocabulary/1370
Project Gutenberg: http://www.gutenberg.org/
Library of Congress: http://www.read.gov/
Sports Illustrated for Kids: https://www.sikids.com/
Tween Tribune: https://www.tweentribune.com/