This is a great website that offers all the resources you need to grow professionally. It has different sections with each one full of PDFs, books, articles an many more .
http://www.educationworld.com/

Discovery Education provides high quality, dynamic, digital content to everyone be it a teacher, an administrator,student or even parents.
http://school.discoveryeducation.com/schrockguide/?campaign=DE&CFID=2886098&CFTOKEN=58686871

Ed Week is a also one of the leading websites in education. It helps teachers and educators grow professionally by providing all kinds of resources for free.
http://www.edweek.org/tsb/index.html

EPD is the largest online database of professional development conferences and workshops for educators and teachers from Early Learning to Grade 12.
http://www.educatorsprofessionaldevelopment.com/

This is a free professional development platform from Intel that provides a series of compelling courses on the 21st century learning concepts.
http://www.intel.com/content/www/us/en/education/k12/teach-elements.html

Teacher Trap is a free , professional development resource that helps educators and librarians address common questions about the use of technology in teaching and learning by providing easy access to practical, online resources and activities.
http://eduscapes.com/tap/