I've been with Microsoft since we got our first 'real' computer...back then it was MS-DOS, then Windows 3.1, which held records for Most Blue Screens in a Single Hour. We struggled through a few more versions with varying degrees of satisfaction, then settled in for a nice, long and fairly successful trip with XP Pro.
I don't use Windows as much anymore, and if the summer's crop of annoying minor illnesses hadn't slowed me down, I'd be a nearly-full-time Linux user. Linux is easy, intuitive, and fun. It has much better security, excellent support, reliability (I have yet to see a blue screen!), and...it's free!! So are the programs that run on it!! Linux also works on machines that can't handle Windows easily. A program called Wine even allows me to run most Windows programs in Linux!
The basic Linux programs and their add-ons, games, educational programs, etc. are all free. To be sure, some do sell Linux, but they are peddling their own support and such. The programs themselves are all free, and excellent tech support is available free at Ubuntu Forums. That is one of the main reasons why schools all over the world are switching to Linux.
In a way, switching to Linux is a bit like embarking on the waters of homeschooling: we stop relying on a larger entity to do it all for us, and start becoming more self-reliant.
Edubuntu - the educator's version of Linux. Check out these screenshots
Linux for Education - Links and resources for Linux
Schoolforge UK - Lists open source software for Linux, Windows and other systems. Also has a list of educational programs with Wine.
Schooltool - Useful teacher programs...lesson planners, record books, etc.
The KDE Education Project - Developers of Linux educational progams (and they are free!)
Thornburg Center - listing of Linux programs and resources for educators
Technology and Learning