You've probably heard of Linux. Analysts at The Gartner Group have predicted that

Linux may be the majority server operating system by the year 2008. IDC, another analyst group has predicted that Linux will gain desktop market share at an even faster pace.
From Windows to Linux will give you a brief overview of Linux from a Windows user's point of view. We will teach you how to make the move from Windows to Linux easy in a friendly conversational style. You will install Linux and use it's many applications such as OpenOffice, Gimp, Evolution and Mozilla to accomplish tasks that you would normally use Word, Photoshop, Outlook and Internet Explorer for on Windows. Included is the 600 page book quot;
Moving from Windows to Linux" and a full version of Linux including the OpenOffice suite, Mozilla, and 2000 other applications for free!