A new edition of Windows Server 2008 got launched yesterday Windows Server 2008 Foundation which will only be shipped on a range of appropriate servers. It supports 15 users, 8gb RAM and 1 processor (but no core limit).
I can see that many small business might want to use this as their central server where they may have some of their data in the cloud (the obvious example being e-mail) but want some information such as the company accounts on premise. I can also see Foundation as being a logical home for SQL Express or Workgroup edition, probably bought along with the aforementioned accounts or a small ERP system.
Companies wanting to do a little bit more on premise would probably be better off with Small Business Server (SBS) which has exchange and SQL Server built in as well as a basic set of tools for monitoring the health and security of the server and the PC attached to it.
As a final thought even though April 1st was yesterday, I wonder if this would be a good platform to host LAN parties!