Great list of different educational networks in many different formats, including diigo, Linked In, Facebook, nings, wikis, and more. Some are by discipline
Kathy Schrock has an extensive guide to the best websites. This particular page summarizes the sites she has recommended in the past. (It started more as daily, and is more like weekly now.) Her entire site is very organized, and has something for every discipline.
Interesting list-- includes educators from many different walks, including some in specific disciplines. Click on a name to learn how to connect with them.
List of resources curated by a superintendent, with input from others. Includes explanatory flash cards and a variety of categories to include many disciplines.10-2-17