This particular entry addresses twitter, but there are many great things on this blog. How cool that a husband and wife blog together (can't imagine that happening at my house!) They include various resources, including history and elementary ed.
Learner Express is a gallery of short video modules distilled from over 350 hours in the Annenberg Learner Collection. The science topics are useful in a STEM-based curriculum, while the math topics align with the Common Core Standards. You can quickly locate 1-5 minute videos to enhance classroom or professional learning. Indexed, annotated, and linked to related resources,
Recordings of LiveClass2.0 webinars. These orginate at noon on Saturdays. Fabulous livebinders are created for each show. They are moving them over from another site, so not all are here as yet.