Doorstop - Requirements management using version control.
rmtoo - rmtoo is a free and open source requirements management tool.
Traceable Requirement Management - Product Managers and Requirement Engineers need to efficiently capture and communicate the "voice of the customer", to enable their organization to deliver the right offers at the right time.
Reqflow - Reqflow is a free and open-source tool for traceability of requirements across documents, designed to analyse documents with speed and efficiency.
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.
Modern Requirements Suite4TFS - Modern Requirements Suite4TFS is an innovative, efficient and collaborative requirements management tool.