Flowlingo - Get fluent in a language through content immersion

Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.

Eduflow - Digital learning that actually teaches students something

Groups.io - Email and web based discussion group software, includes archiving, emails, wiki, polls, file...

Padlet - Visual boards for organizing anything.

Gaggle Mail - Gaggle Mail is a simple and easy to use email list manager.