Achievo is a Web-based project management and tracking tool for small- to medium-sized companies, aiming to become a fully featured ERP-like system in the future. Features include a time registration module, scheduler, project management, todo's, and several statistical tools. Achievo is multi-language, fully customizable, and uses a modular system to allow future extensions.
Calcium provides interactive calendars you can use through your browser. Features include: dynamic calendar merging (events from one calendar can be included in another), multiple views and formats, repeating events, email support, extensive color and font customization, support for full HTML in the event text and calendar headers and footers, popup text associated with any event, searching and filtering, multi-language support, a flexible security model, and more. Calcium is very easy to use, and fully supported by an established company. It runs anywhere that supports Perl CGIs; no non-standard Perl modules are necessary. Full 2-way synchronization with Palm Pilots or MS Outlook is available; iCalendar "subscriptions" are supported too.
Calendars for the Web provides a server based calendar and scheduling application. It allows unlimited users to share unlimted events per calendar. Calendars for the Web comes with a full-featured browser based interface, is completely customizable (sixteen different calendar view types), fully documented, and supports online administration.
Celebrat is a very easy-to-use, non-interactive, text-mode calendar application. It reads a data file in ASCII format, and prints on stdout a human-language summary of what events will take place up to ten days from now. It also includes a small daemon which announces events that are due by putting a message on every registered terminal, or by integrating the announcement in the bottom line of GNU screen sessions.
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.
E*Reminders is a series of PHP scripts that interact with a MySQL database to setup email reminders for any events or occasions you'd like. It includes recurring reminders, advance notices, and password authentication for email addresses. It can be used for an entire company, as a service for Internet users on your site, or privately.