Khan Academy offers instruction as well as assessment on a range of topics from basic numeracy and literacy to Psychics and Astronomy. The program delivers content in an easy to understand and interactive manner and assess in a more engaging way. Great for remedial learning as well as advanced students. Log-in required
Engage NY Is a website by the New York Department of Education. The link included is to a list of lessons for all grades in both English and Math. The lessons include resources like instruction guides, printouts, activity cards, and posters. The whole websites is useful and has a lot of resources like a Math and English toolkit for the common core.
Teachers Pay Teachers
This website has well made resources for free and for pay. The resources were created by teachers for teachers but are accessible to everyone. Requires a login.