Uncle Unc is a framework for working with trees of objects. Existing services such as filesystems, code libraries, networks, log files, mailboxes and directories can be mapped onto this object tree, as can some traditional desktop applications. User interfaces work directly with the object tree, offering best of breed interface design (e.g. filtering, breadcrumb bars, paging, sorting, and file-explorer-like views) across the full range of services. The framework promotes clean design, completeness of representation, and reusability of both front end and back end code.
SwiXAT is a Swing-based authoring tool for the quick and easy development of GUI Java applications. It implements a true MVC framework and uses XML to define the view (SwiXML is used as the XUL engine), BeanShell as a scripting language for the controller, and JXPath as the binding mechanism between the view and model. It provides a complete environment in which it is possible to almost write an entire Java Swing application without writing Java compiled code. The use of XPath makes it very simple to traverse the object tree of the application's business model.
Red-Piranha is a search system that can actually learn what you are looking for. It can be used as a Web page, command line, or XML-WebService, so it will work with most languages, including Java, Perl, C#/.NET, and PHP. It includes learning abilities for the Desktop/Internet search functionality. All feedback from the user is stored in (editable) XML and RDF, and is used by the system to improve the quality of searches.
Apollo is an open-source developer test skeleton toolkit for Java Web Start/JNLP. It lets you turbo-charge Web Start apps without Web Start to speed up your compile/run/test/debug/goof-off cycle, avoiding the hassle of stuffing, signing, uploading, or downloading your jars every time you rearrange a comma in your source code.