phlyMail is a groupware, webmailer, and PIM. It offers unlimited nested groups, unlimited POP3/IMAP profiles, quotas, an integrated address book, a calendar with multiple reminders and event repetitions, a file manager with an integrated WebDAV server, the ability to send faxes, SMS support (which lets you send SMS, get reminded of events via SMS, and get email notification via SMS), a bookmark manager, themes, and multilingual support. It uses either sendmail or SMTP to send email, and can handle MIME and SSL connections. Support for IDN (Internationalized Domain Names) is included. Through its modular design, it's easy to add completely new features as modules, which can be plugged into the system.
Calcurse is a text-based calendar and scheduling application. It helps keep track of events, appointments, and everyday tasks. A configurable notification system reminds the user of upcoming deadlines, and the curses based interface can be customized to suit user needs. All of the commands are documented within an online help system.
Wieldy is a to-do list manager that is based on the principles of GTD (Getting Things Done). It allows you to manage your to-dos in a simple but effective way. To-dos can be created as thoughts and actions, which can then be assigned to the Next Action, Today, or Someday categories. Tasks can also be scheduled and listed in a calender-like overview, as well as linked to a project or simply put on hold. Wieldy also allows you to manage your contacts and delegate actions to them. Other features include support for data encryption, tagging, priorities, recurring action templates, and synchronization with other PIMs like Outlook. No installation is needed.