ExtremePlanner is Web-based project planning and tracking software that helps development teams collaborate. It's especially useful for distributed teams using Agile processes such as Scrum and Extreme Programming.
The basic idea in agile development methods is to prioritize features (or user stories) with customer input, then deliver software in regular, short iterations (usually 2 to 4 weeks). The quick turnaround helps minimize waste from miscommunications or incomplete specs.
ExtremePlanner lets a development team enter user stories (features or defects), estimate and prioritize them, divide them into tasks, and track progress across multiple releases and iterations. It also helps organize test cases, related files (documents, images, etc.).