Roundcube Webmail is a browser-based, multilingual IMAP client with an application-like user interface. It provides the full functionality you expect from an email client, including MIME support, address book, and folder manipulation. High extensibility is granted by the plugin API and the user interface is fully skinnable using XHTML and CSS 2.
XWiki is a WikiWiki clone written in Java that supports many popular features of other Wikis like the Wiki syntax, version control, attachments, security, and searching, but also many advanced features like templates, database and dynamic development using scripting languages (Velocity, Groovy, Ruby, Python, PHP, and more), an extension system and skinability, J2EE scalability, an XML/RPC remote API, statistics, RSS feeds, PDF exporting, WYSIWYG editing, an Office viewer and importer, and a lot more.
Gollem is a Web-based file manager that provides the ability to fully manage a hierarchical file system stored in a variety of backends such as a SQL database, as part of a real filesystem, or on FTP, Samba or SSH servers. It supports uploading and downloading of files, basic file operations, permissions support, and MIME recognition and viewing of files through the Horde MIME library. It is fully internationalized and translatable.
LogicalDOC is a Web-based document management system that is easy to use and learn. Its architecture leverages best-of-breed Java technology to achieve a powerful and flexible solution. It supports its users with a powerful search engine (Lucene), Web service interface (JAX-WS via CXF) compatible with .NET and PHP, versioning, annotation on documents, a WebDAV interface, importing and exporting from .zip files. Documents can be organized into hierarchical folders, searched using the integrated search engine, or browsed by Tag. The system is extensible thanks to the technologies used (Spring-Hibernate) and its plugin architecture.