Naked Objects is an application development platform. It's called Naked Objects because all you need to develop are your domain objects; the Naked Objects platform automatically creates an object-oriented user interface (giving you the choice of different styles) and the underlying storage mechanism (again, giving you the choice as how to persist your objects).
Google Gadgets for Linux provides a platform for running Google Gadgets under Linux, catering to the unique needs of Linux users. It's compatible with the gadgets written for Google Desktop for Windows as well as the Universal Gadgets on iGoogle. There are two main components to the application: one is a common gadget library responsible for running and presenting a gadget, and the other is a host program that allows the user to choose gadgets and run them on the desktop. Currently it has hosts written for GTK+ and Qt, with the GTK+ host offering a sidebar similiar to that of Google Desktop for Windows.
The WSO2 Mashup Server is a platform for creating, deploying, and consuming Web services Mashups in the simplest fashion possible. It features support for consuming and deploying services using dynamic scripting languages, trivial deployment and redeployment, automatic and UI-based generation of Web services artifacts (e.g., wsdl, schema, policy), a set of gateways into a variety of information sources, including SOAP and POX/REST Web services, as well as plain old Web pages, and human-consumable results through a variety of user interfaces, including Web pages, portals, email, Instant Messenger services, Short Message Service (SMS), etc.
IT Mill Toolkit is a server-side RIA (Rich Internet Application) library that provides a versatile set of AJAX widgets for Java programmers. Applications are programmed in Java and executed server-side. At the client-side (i.e. in the browser), enhanced GWT widgets are used for presentation.
Wicket Web Beans (WWB) is an Apache Wicket component toolkit for displaying and editing POJOs that conform to the JavaBeans specification. Web pages are automatically generated based on bean properties and certain conventions. If necessary, the layout, editability, and actions of these pages can be customized on an exception basis. In other words, the toolkit normally does what you'd expect, but when it doesn't, you can override its behavior.