Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Missive - Team communication app now supporting FB, Twitter & SMS
Slack - A messaging app for teams who see through the Earth!
Spike - Spike solves businesses' communication chaos by bringing together email, team chat, collaborative docs, and meetings, into one feed.
Notion - All-in-one workspace. One tool for your whole team. Write, plan, and get organized.
Mailtrim - Email lives forever!. Reinvigorate your emailing experience with the best free email client, the Mailtrim