Screencastify: Capture, edit and share videos in seconds.
Loom: This screencasting extension is great for teacher use as the recording can quickly be shared with students via gmail or copy/paste.
One Click Timer: A slick and reliable timer app for Google Chrome.
Move It: Add this extension to the browser, set the notification interval, and your screen will present you with a random brain break and exercise to complete.
Glide- Make an App from a Google Sheet. There is a social component if a classroom is using the same app.
Websites:
Classroom Screen: A free and simple/interactive tool with digiboard widgets (i.e. drawing, timer, stoplight, QR codes, etc) to help students focus more on their work.
Plickers: Tool for quick checks for understanding to know whether or not students are understanding the lesson.