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.

CAMPR - Open source project management tool with 16 modules

Nifty - Manage projects, work, and communications in one place.

Confleo - Confleo is an all-in-one project management and CRM tool that allows you to create and manage multiple projects, assign multiple users within it, create stunning invoices for your clients and even accept payments from them through in-built payment g…

GoodGantt - The best Gantt chart for Trello®

SmartSuite - SmartSuite is a collaborative work management platform that enables teams to plan, track and manage workflows, projects and everyday tasks.