OpenGroupware.org is a set of applications for contact, appointment, project, and content management. It is comparable to Exchange and SharePoint. It is accessible using Web interfaces or using local clients via WebDAV, GroupDAV, and CalDAV. Custom applications can be developed using the XML-RPC API. OpenGroupware.org runs on almost every GNU/Linux system.
Tobedone is a Web-based Java applet project management tool which organizes complex projects in tree structures and offers you many manipulation tools. You can give specific tasks priorities, assign them to persons, create and delete databases, give permissions to users, sort project tasks by priorities, dates, etc, and a lot more.
ToutDoux is a project manager for GNOME. The approach of data manipulation is abstract (database free). It's extensible with plugins. Most tasks are and will be subcontracted with commandline frontends. The file format is XML (including a schema, plugins parameters, and datatables).
ttm is a simple but flexible command-line based Perl program for managing lists of tasks. Arbitrary properties can be attached to each task. Standard properties such as `priority', `status' and `categories' are used to provide different ways of viewing the task list. Editing is done with your favourite text editor.
TUTOS (The Ultimate Team Organization Software) is a groupware, ERP (Enterprise Resource Planing), CRM (Customer Relationship Management), and PLM (Project Lifecycle Management) suite that helps small to medium teams manage various things in one place. Its features include personal and group calendars, an address book, product and project management, bug tracking, installation management, test management, scrum management, a task list, notes, files, mailboxes, and useful links between all of the above.
Vanilla is a WikiClone written in REBOL. It is useful for collaboratively working on projects, tracking todo items, managing adresses, and creating Web logs. All page editing takes place in the browser. Vanilla features a simple templating system, a full-featured user and session management system, and an extension architecture for writing simple Web applications in REBOL.
Wcal is a Web-based calendar and planner especially suitable for multi-user setups in an intranet. It features the ability for several users to have their own or shared calendars, read-only views, Weekly and monthly repeating events. It uses the Web server's access control methods, and allows a separate access control definition for each user.
WebCal is a free browser-based calendar program to help you keep track of your appointments, meetings, birthdays, etc. It's simple, yet has powerful scheduling features, email reminders, and a user-friendly interface, and being Web-based makes it ideal for use by groups of people.
WebCalendar is a Web-based calendar application that can be configured as a single-user calendar, a multi-user calendar for groups of users, or as an event calendar viewable by visitors. WebCalendar requires a database such as MySQL, Oracle, PostgreSQL, MS SQL Server, ODBC, or Interbase. Features include email reminders, iCal/vCal import/export, remote subscriptions for Sunbird or Apple iCal, LDAP and NIS support, and translations for 29 languages.