HEY - Email at its best, new from Basecamp.
Houseparty - Brining empathy to online communication.
InstAddr - Disposable email address application.
Booyah - Video chat with up to 12 friends at the same time.
Horde - Horde Groupware is a free, enterprise ready, browser based collaboration suite.
Slack - A messaging app for teams who see through the Earth!