Great website for all grade levels. There are blogs from other teachers and different resources for the classroom. You can also find important information about schools.
This foundation offers programs for students "to think of mathematics like never before." This website offers resources to assist teachers in teaching in new ways.
This resource is not only helpful for educators, but for parents as well. The specific article I am referring to provides parents with a detailed list of hints for homework-help and home-front strategies to get the most out of homework and study time (maybe a great "packet" to hand out at open-house =D ).
This website allows you to look up audio, videos, worksheets, and lessons based on your topic/ unit. The site will even filter by grade level and subject and will give you different lesson plans/ worksheets you can use in the class. They also have interactive games for the lesson that students can do online.
This website is a resource for teachers to learn about new methods of teaching, what works best, and there is even a blog. This website is also broken down by topic area.