So one of the proposed solutions at work to our information lack-of-management is to use eGroupWare. It looked interesting, so I've installed it here.
One thing which immediately comes to mind is the fact that this is a heavy application -- it is almost unusably slow on jupiter. The whole thing is also very obviously not written in english first, although the translation is fairly competent. The intra-user sharing is very ACL heavy, meaning that (necessary) setup isn't quick, and the whole thing is frustrating when run on such a slow computer. And some of the sub-applications (such as the address book) are excessively detailed, too much so for home use.
Although an interesting idea, I think that for home this is a non-starter until we have a more powerful computer to run it on.