Freehelpdesk is feature-rich help desk system designed from the ground up to meet the demands of help desk staff and their users. It is a Web-based system that can accept new calls from your users directly into the system. Calls can be tracked and searched to enable faster response times.
OTRS is a platform independent Web-based help desk system that supports service organization of any kind (e.g. IT service, customer and technical product service, complaint management, public services, etc.) to increase their efficiency. It increases transparency as well as service quality and lowers your total cost of ownership. It has been certified ITIL V3 compatible by PinkVERIFY for incident, problem, change, service asset and configuration, request fulfillment, and knowledge management. Other ITIL processes like service catalog and service level management are supported as well.
BORG is a calendar and task tracking system written entirely in Java. The calendar is an appointment organizer that provides a nice month view, month printing, email reminders, popup reminders, and a to do list. The task tracker tracks issues and tasks through various user-defined states.
Haystack is a powerful tool designed to enable each and every individual manage all of her information in the way that makes the most sense. By removing the arbitrary barriers created by applications that only handle certain information "types", and recording only a fixed set of relationships defined by the developer, users can define whichever arrangements of, connections between, and views of information they find most effective. Such personalization of information management will dramatically improve your ability to find what you need when you need it.
MailManager helps teams deal with large volumes of email by allocating mail to the right person, providing tools to help answer it (prioritisation, reply templates, and a knowledge base), and allowing managers to set service levels for different types of mail and report on performance against service levels and volumes received. MailManager is based on Zope which is required to use it. It is cross-platform, but most of the testing has been under Linux and Mac OS X.
Copper is a Web-based project management software tool designed to help creative teams manage clients, projects, tasks, files, budgets, and events. It has an HTML/AJAX front end. It is available with full source for a licence fee or as a SAAS hosted service (compatible with iPhone, but available via PC/Mac/Linux and a Web browser).