Atlas Essentials (Free)

Atlas is a web-based requirements management tool that enables you to manage projects in a way that is more collaborative and flexible than existing requirements management tools. Atlas helps you to quickly take ideas and inspiration in the form of various visual elements, attach those ideas to a Whiteboard, then organize into Plans that can easily be tracked via the Delivery Backlog. It also facilitates easy collaboration with peers so that you can formalize Requirements and then pass those Requirements across to development teams.