Serena Dimensions RM - Serena Dimensions RM is a web application to improve the definition and management of requirements across the product lifecycle.
Beyond Compare - Beyond Compare allows you to compare files and folders.
ReqView - Simple and powerful requirements management tool enabling easy requirements gathering, traceability tracking and offline collaboration.
WinMerge - WinMerge is an open source differencing and merging tool for Windows.
Visure - Visure offers a flexible , modern and complete requirements ALM Platform (Application Lifecycle Management).
Meld - What is Meld? Meld is a visual diff and merge tool targeted at developers.