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Pearltrees is a great, free site I wrote about in January that lets you organize web content in a visual pattern. There is a Chrome browser extension that makes it easy to add sites to your tree. Trees can be shared and even worked on collaboratively.
A member of my PLN (sorry, can't remember who now and I forgot to make a note of it) just shared a great Pearltree: "Ben's Guide to the U.S. Government for Kids."
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The resources are sorted by grades: K-2, 3-5, 6-8, 9-12 and there is a page about Ben and a Parent and Educator section. Each section has information, links and resources about the US Government. This is a great resource for anyone teaching, or learning, about the US Government and how it works.
Here's the main page for 9-12:
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This is a great example of how a tool like Pearltrees can be used to create educational resources for students (or even have students create them as a project)