Back in 2008, Microsoft rolled out the DreamSpark program as a means to get Microsoft software design and development tools in the hands of students at no charge. It was initially only for university or college students, but it has been expanded to also cover high school students. Basically, this means that any high school, college student, or faculty member (in most major countries) can download copies of many Microsoft operating systems, servers, and development tools for free. If you fall into one of those categories, it is pretty easy to get signed up and verified into the program, so you can get your hands on the software for free.
Some of the most valuable items are Visual Studio 2010 Professional, Windows Server 2008 R2 Standard, and SQL Server 2008 R2 Developer Edition. The Microsoft DreamSpark site has more details about the program.