Whenever someone tells me there is no choice of software in the Office or Groupware category I assume they are sadly underinformed. Actually there is a dizzying choice once you get beyong market leaders like MS Office 2007 in the Office category and MS Exchange/SharePoint and IBM/Lotus Notes/Domino in the Groupware category. Some are from big, well-known companies; others are, no doubt, from a few programmers in a back bedroom. Nevertheless, some of them have attracted substantial followings, both on traditional (behind the firewall) platforms and in the cloud.
Today, an article on ZDNet took me to http://www.fileheap.com/software/groupware_software.html where I discovered piles of downloadable groupware, some free, some at a (low) fee. Often, fee-paid products were available for a free trial. Of course, free office software is everywhere, from IBM's downloadable Symphony suite to on-line offerings from Google and Zoho. An extensive listing of Web 2.0 Office software, courtesy of Ismael Ghalimi, can be found at http://itredux.com/office-20/database/.
This is a different view of what's available, of course. It may not be suitable for the biggest companies who want formal support or proof of years of working with large enterprises. Nevertheless, it is a fertile place to observe what is happening and what is possible.