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.
Freelancer Stack - Curated directory of tools used by 10,000+ freelancers
Coworkly - Coworkly is a free tool for creative contractors to put freelance bookings, payments, & work goals on auto-pilot!It's a portfolio, scope of work, & invoice bundled into one simple flow that allows clients to reserve your time in a few easy steps.
The Standard Freelance Contract - The first common standard service agreement
Microsoft Planner - Microsoft Planner lets you easily bring together teams, tasks, documents, and conversations for better results.
Freelancelift - Community, training and support specifically for freelancers