Starting today, $999 gets you a Mac mini with quite respectable specs, preloaded with Mac OS X 10.6 Server (unlimited license). While this combination is potent enough for far more strenuous use, it practically screams workgroup, since it's easily affordable enough to allow sprinkling them around a company, and compact enough to fit into a drawer, if need be.
Mac OS X 10.6 Server combines the power and security of UNIX with the ease of use of a Macintosh, and comes with a set of collaboration tools to help people communicate and help organizations learn.
This is an amazing deal! (And you thought Macs were expensive...)