Visure - Visure offers  a flexible , modern and complete requirements ALM Platform (Application Lifecycle Management).

rmtoo - rmtoo is a free and open source requirements management tool.

Valispace - Valispace is a modern browser based tool for complex hardware development that connects data for engineers, efficiently manages requirements and much more.

Rational RequisitePro - The list below identifies the supported releases of IBM Rational RequisitePro from which you can select system requirements in different levels and organization of detail.

Jama - Jama combines requirement management software with enterprise collaboration capabilities to solve product delivery problems.

Doorstop - Requirements management using version control.