Documize - Enterprise-grade wiki and knowledge management platform

Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.

HackMD - Fast and flexible, real-time collaborative markdown, inspired by Hackpad.

Basecamp - A simple and elegant project management system.

ReadTheDocs - Spend your time on writing high quality documentation, not on the tools to make your documentation work.

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.