If you are looking for an open source groupware suite, then consider using PHProjekt which is modular and it allows groups using the Web to co-ordinate events as well as information and documents. In fact, PHProjekt also has several components that users will find especially useful including a group's calendar, ability to manage projects as well as time tracking feature and even the ability to manage documents. Also, there is a contact manager and mail client as well as a host of other modules that can suit you whenever the need to use them arises.
PHProjekt is also able to support a number of protocols of which LDAP and Soap as well as Webdav is good examples and the application is also available in as many as thirty-eight languages and there are also nine databases that can be used.
The best part about using PHProjekt is that users can add whichever modules they require to complete specific tasks or projects, and PHProjekt is also a simple system that can be used for a team of professionals without being complicated or having redundant features that will use up your memory as well as waste time.
To use PHProjekt, you must have a web server that supports PHP and also MySQL and it also has a project structure tree which is sub-divided into smaller projects and to which you can add as many tasks as you want. In fact, PHProjekt is also well known for having a very advanced set of calendar modules as well.
There are also team manager/contact modules as too support and request trackers and also a note system that make PHProjekt very effective. However, it is not to say that PHProjekt is perfect as its modularity can often prove to be a bit complicated, while there may also be some modules that won't be compatible with the system you are using.