http://www.readwritethink.org/ - Providing educators and students access to the highest quality practices and resources in reading and language arts instruction.
http://www.proteacher.net/ - A professional community and web directory for teachers in grades PreK-8.This site includes free lesson plans and discussions for elementary and middle school.
https://www.teachingchannel.org/ - Teaching Channel is a video showcase of inspiring and effective teaching practices in America's schools. It includes sample Common Core video lessons and ideas in all subject areas and grade levels.
http://www.sharemylesson.com/article.aspx?storyCode=50000148 - Developed by teachers for teachers, this site offers a free platform that gives access to teaching resources and tools and provides an online community for teacher collaboration. The site has a significant collection of CCSS-related resources, covering all the aspects of the standards. It includes K-8 Math and 6-12 Language Arts Common Core aligned resources. Users will need to create a free account to access some of the resources.
www.learnzillion.com - LearnZillion is a free learning platform that combines video lessons, assessments, and progress reporting. Each lesson highlights a Common Core standard, in either Math or Language Arts.