Teachers Pay Teachers - This website offers a variety of paid and free resources for teachers. They offer lesson plans, activities, posters, projects and so much more all published by teachers.
Super Teacher Worksheets - This website offers a huge selection of worksheets for elementary school classrooms in almost any subject you can imagine!
Read, Write, Think - On this site teachers can find tons of lesson plans. They also have a section that offers professional development for teachers.
Mrs. Renz's Class - This site is a blog by a fourth grade teacher. She a variety of things to offer for her students but also for fellow teachers such as her awards and recognitions, classroom ideas, and a look at her own classroom.
Survival Guide for New Teachers - The U.S. Department of Education of put together a collection of resources for first years teachers. Most of these resources come from veteran teachers.
Teach Hub - This website offers a diverse collection of resources. These include lesson plans, worksheets and acitivities, articles, professional development, and information about graduate programs.
Edutopia - This website offers lots of articles and videos on a variety of subjects for teachers.