Citadel is an advanced messaging and collaboration system for groupware and BBS applications. Users can connect to Citadel using any telnet, WWW, or client software. Among the features supported are public and private message bases (rooms), electronic mail, real-time chat, paging, shared calendaring, address books, mailing lists, and more. Unlike other collaboration servers, Citadel provides its own data stores and is therefore extremely easy to install; you don't have to "bring your own" email and database because they're built in. The server is multithreaded and scalable. In addition, SMTP, IMAP, and POP3 servers are built-in for easy connection to Internet mail. Citadel is both robust and mature; it has been in production since 1987.
NullLogic Groupware is a modular Web-based groupware and email system designed for contact management and event scheduling. Additional features include private messaging, public discussion forums, webmail, shared bookmarks, file sharing, call tracking, order processing, an XML-RPC API, and integrated POP3 and SMTP servers.
Minkowsky is a combination of a calendar, address book, and task management software. It is a client/server application; all data is managed on a server and displayed on the client. It was designed to manage calendars for small-to-mid-sized groups, so it lets you look into other calendars to check who is available for a meeting. To each address in the address book, a memo pad is associated to take memos about phone calls, etc.
Comment is a command line directory context note taker. Notes are stored in both the local directory and each users home. It was developed as a low impact tool for retaining flyaway information that is often needed at a later date. The dual storage system provides convenient access to prior notes, and all notes are stored in plain-text format.
Chandler is a standards-based "Note-to-Self Organizer" designed for personal and small-group task management and calendaring. It consists of a desktop application and Chandler Hub, a free sharing service and Web application. You can also download and run your own Chandler Server.
OpenXAdES enables people to work with legally-binding digital signatures (primarily giving and verifying them). Legislation often defines a set of requirements that legal digital signature technologies and infrastructures must be compliant with, and OpenXAdES aims at meeting many, if not all, such requirements from different legislations.