1. Web based GroupWare system written in PHP phpGroupWare is a web based GroupWare system. It comes with several core apps for email, calendar, todo list, address book, file manager, and a notepad. It also provides a framework for add-on modules to integrate seamlessly in phpGroupWare. Some samples are a bookmark manager, a trouble ticket system, a weather reporter, a phone log, a chat program, and a forum system. There are many more in development, and you can develop your own as well. You should use it if you would like a powerful groupware system that can be access from anywhere on the Internet, and allows for custom add-ons. For companies with a distributed user base, it's an ideal solution. Oh, and did I mention that its FREE? From Debian 3.0r0 APT