If you turn it on in MS Excel you can scroll the sheet with the arrow keys in stead of moving the cell pointer.
There is a Drupal distribution built specifically for that purpose: http://openatrium.com/ There's a lengthy article about it in the December issue of Linux magazine: http://developmentseed.org/blog/2009/nov/09/open-atrium-featured-linux-magazine which should help you get started.
It features groups, calenders, blogs, documentation and an issue/task tracker right out of the box.
The easiest solution for setting up your own jabber server is to sign up for Google Apps with your domain (http://www.google.com/a/) activate talk and then you can connect with any Jabber client to the google servers, eg. with Kopete: http://www.google.com/support/talk/bin/answer.py?hl=en&answer=57557
You even have the option to limit communications within your own domain or to allow users to chat with other users outside of your domain.