Front-end designers, project managers, and clients consistently ask Drupal engineers for clickable wireframes early in the development cycle. When developing "agilely", this is particularly important. Unfortunately, it's not always easy to manage placeholder page content in Drupal. Often it's done by creating placeholder nodes, but that requires either maintaining database dumps containing these nodes, or creating them on the fly with install scripts.
Wireframe Me attempts to address this issue in a light-weight and codified manner by providing a simple configuration file, similar to a .info file, for creating/managing placeholder URL paths, page titles, and page body content.
Interestingly, this module leverages Drupal 7's new hook_module_implements_alter function such that the paths/pages created by this module are overridden quietly when another module, node, or view creates a path with the same URL.
Since really any value can be returned for the page body, you can simply embed images of mocked-up content/functionality that you've yet to implement. You can also "get started" hanging blocks on these stubbed out pages by combining this approach with the Context, Boxes, and Views modules.
This work was made possible by the good "Agile" folks at Meedan, who consistently support new ways to do "feature-driven" Drupal development.