FUDforum is a templatable forum with i18n support based on PHP and either MySQL, Oracle, PostgreSQL, or SQLite. It features a user/group management system, a multi-lingual spell checker, both flat and thread message views, a private messaging system with multi-user forwarding capabilities, poll file attachments, and much more. It is an extremely fast and scalable forum that can fulfil the needs of both small and large forum operators.
Thunderbird is a total redesign of the Mozilla mail component to produce a cross-platform, stand-alone mail application using the XUL user interface language. It has many new features, among them the ability to customize your toolbars the way you want them. a new look and feel with a large number of downloadable themes which alter the appearance of the client, and the ability to add UI extensions.
Wammu is a mobile phone manager that uses Gammu as its backend. It works with any phone that Gammu supports, including many models from Nokia, Siemens, and Alcatel. It has complete support (read, edit, delete, copy) for contacts, todo, and calendar. It can read, save, and send SMS. It includes an SMS composer for multi-part SMS messages, and it can display SMS messages that include pictures. Currently, only text and predefined bitmaps or sounds can be edited in the SMS composer. It can export messages to an IMAP4 server (or other email storage).
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.