VisualSitemaps is a sitemap generator that crawls a URL you provide and creates a sitemap including screenshots of each page. You can specify the number of pages and depth to crawl and filter out paths. The sitemap can be arranged in horizontal or vertical orientation, shared and exported as PDF. CSV export, re-organization, and comments are forthcoming features.
Exploring the sitemap is a smooth experience. Expand a node to view a fullsize screenshot. The visual representation seems to work well for narrow branches, where the number of children is limited. For broad branches this visualization may be a little overwhelming. Perhaps the service will feature collapsing of branches in the future to make those kinds of trees more navigable. More complex trees might benefit from a radial orientation.
Looks like a useful tool for visualizing sites or web apps.