Slack News Feed - Get the top posts from every Slack chat you're in.
BookWidgets - BookWidgets is an excellent application that let you create engaging exercises in minutes and easily share a varied variety of beautiful and fun activities with your classroom and others.
Lurchr - Saves all your Slack links, so you can focus on work
Padlet - Visual boards for organizing anything.
Slack It - A bookmarklet to share links in Slack with one click
Quizlet - Quizlet allows you to review and create flashcards for a variety of subjects, such as math and reading.