The ApPHP Calendar (ApPHP CAL) is a powerful PHP calendar script that may be easily integrated and used with various PHP projects, such as schedulers, event processors etc. The calendar is very simple to install, implement, and use. It has a user-friendly interface and navigation. It can be viewed in various ways: yearly, monthly, weekly, and daily.
Googsystray is a system tray app for Google Voice, GMail, Google Calendar, Google Reader, and Google Docs. It lets you keep track of the information provided by those services without having to keep a bunch of Web pages open or constantly checking them. It notifies you of new events, such as messages or alerts, and provides basic services quickly.
Easy Weekly Calendar is a PHP class that can be used to show calendar of a given week. It takes the day, month, and year of a given date and generates an HTML table with the days of the week of the given day. The class also generates links to browse to the previous and the next weeks.
GCalert will access all your Google calendars and display alarms via libnotify for whenever you have alarms set for each event. These alarm widgets do not receive focus (and thus do not take keyboard input away from other applications), yet are clearly visible even on a cluttered desktop.
Synovel Collabsuite provides email, calendaring, and instant messaging solution for enterprises. It consists of a Linux email server with calendar and IM, a Web-based administration panel, a desktop client suite that runs on Windows and Linux, and AJAX-based Web mail access. It uses open standards for communications: IMAP, POP, and SMTP for email, CalDav for calendaring, and Jabber for IM.