DHTML Tree is useful as a site menu, an Explorer-style tree, or to display other hierarchical data. Unlike other trees where data is defined in Javascript, data is defined in HTML using familiar tags. This makes setting up a tree easy, provides flexibility in customizing the tree's look and feel, and makes it easy for search engines to crawl the tree and follow links. Additionally the tree tree has wide browser support, and a wizard for easy setup.
The Zapatec Javascript Calendar lets users pick a date from either a popup or flat (in the page) calendar. It has wide browser support, tooltips, the ability to choose time as well as dates, and much more. Customization includes the ability to chose a theme, a language, positioning, etc. The calendar includes a wizard that makes it easy to customize it, so that you don't need to jump into the code.