jSieve is a Java implementation of the Sieve mail filtering language defined by RFC 3028. Sieve is an extensible mail filtering language. Its limited expressiveness (no loops or variables and no tests with side effects) allows user created scripts to be run safely on email servers. Sieve is targeted at the final delivery phase (where an incoming email is transferred to a user's mailbox). jSieve is implemented as a language processor that can be plugged into any Internet mail application to add Sieve support.
Apache SpamAssassin is an extensible email filter that is used to identify spam. Once identified, the mail can then be optionally tagged as spam for later filtering. It provides a command line tool to perform filtering, a client-server system to filter large volumes of mail, and Mail::SpamAssassin, a set of Perl modules allowing Apache SpamAssassin to be used in a wide variety of email systems.
AtMail is a webmail client. The project aims to provide an elegant client for existing IMAP mailservers, with less bloat and a focus on an intuitive, simple user interface. Features include complete Webmail functionality, address-book support, video mail, an AJAX interface, drag'n'drop, and more.
Cosmo is the OSAF calendar sharing server. With your favorite calendar program (Chandler, Apple iCal, Mozilla Sunbird, or any other WebDAV or CalDAV enabled client), you can share your calendar with other people by publishing it to Cosmo. Your shared calendars can be subscribed to and updated by anyone, even if they don't have an account on your server. Cosmo provides Atom feeds for shared calendars, so you can track updates in your favorite feed reader and integrate your calendar into your Web site or blog.
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.
Echomine Feridian is an easy-to-use Java API that gives you quick and easy access to the XMPP network used in IM services such as Google Talk. The API allows you to communicate with Jabber/XMPP servers for sending and receiving instant messages, presence management, and custom extensions to the XMPP protocol.