Groupware/collaboration software enables groups to work as a team and share knowledge effectively. I cannot stress enough the importance of these technologies. Groupware will prove to be a reliable method of learning and working for all mankind. How we will levereage shared knowledge to its best advantadge. Modern communication requirements mean that just email is superceded..
Below are some links to the most popular groupware, if you take a look you will see they are quite different and will meet the varied needs of any business.
As you can see from this selection of popular open source groupware there are many different ways of working together. I would avoid Zimbra though as it is expensive on resources. I installed on a virtual server with 4GB of RAM and it could not function. It requires a minimum of 8GB RAM and I do not think it likes virtual servers so requires a physical server. This is a step backwards as the advantage of virtual servers is they are hardware independent. If the physical server the virtual servers are on dies, you simply move the virtual servers to another different even, physical server.