Luxor is an open-source XML User Interface Language (XUL) toolkit in Java that lets you build UIs using XML and also includes an ultra light-weight, multi-threaded Web server, a portal engine, and a template engine. It is also Web Start-ready, as everything fits in a jar and requires no loose files.
BitNami RubyStack provides a fast, easy way to develop and deploy Ruby on Rails applications. It includes Ruby, Subversion, MySQL, SQLite, ImageMagick, and several Ruby Gems, and will optionally install Apache 2.2 with rewrite and proxy support. It supports Windows, Linux, and OS X, so you can share the same Rails environment on multiple platforms.
Rachel is a resource loading toolkit for Java Web Start/JNLP. Rachel offers two solutions that make resource loading for Java Web Start/JNLP apps easy again. Solution 1 installs a URL handler for a new protocol called class:// that delivers content from jars identified by a Java class. Solution 2 embeds a multi-threaded ultra-lightweight Web server in your app that serves up content from jars in the Java Web Start application cache. Rachel also works without Java Web Start, although this might be pointless. Examples and user documentation are provided.
The Darwin Calendar Server is a standards-compliant server that allows multiple users to collaboratively share calendaring information. It provides a shared location on the network to store schedules, and allows users to send each other and manage invitations. In order to provide interoperability with multiple calendaring clients, the server implements the CalDAV protocol, which is an extension of WebDAV, which is in turn an extension of HTTP.