This rich (and free) resource provides examples for most of the CCSS math standards to include lessons, example problems, and more.
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CCSS math activities! Drill down to the individual standards to find thousands of online activities mapped to the standards. There are some wonderful tools and actvities here to discover.
A zoomable visual demonstration of scale. Zoom in all the way to Plank length and out to the whole of the observable universe. This would be an excellent jumping off point for student writing, discussion, and thinking in a science (or math) class. Another wonderful interactive visual demonstration from Cary and Michael Huang.
Very cool math and science quiz type website. Allows players to select grade level, subject area, or skill/objective. Gives MCT type multiple choice questions and offers explanations for missed questions.
This is an excellent collection of short videos demonstrating real classrooms with real teachers and real students. There are currently 157 clips in the Common Core topic across all grades and subject areas. There are great teaching ideas here. The videos of lessons also often include the materials for the lesson such as lesson plans, handouts, slides, etc.
With 100 specialized search engines for academic research listed, you are certain to find some new ones. Some of my favorites are included in this list. The list is organized into helpful catagories by subject or discipline. One of my favorites for History is listed here, the David Rumsey Historical Map Collection. The collection has over 30,000 images, searchable by keyword.