Chalk - Chalk is a calculator that tries to do right what others do wrong.
Loom - Loom is a screen recording extension for Chrome that gives people the ability to create and share media. Create your own videos using your camera, screen view, and audio. Read more about Loom.
Public - Group chats.
Kap - Kap is an open-source screen recorder built with web technology.
Slaask - Slaask enables you to set up a dedicated live chat channel on your Slack.
Screencast-O-Matic - Free version Records up to 15 minutes, premium is $15/year.