I run Windows 7 on a Mountain Lion MBA and Power Mac, mainly to use Quicken for my financial data. Bootcamp, as mentioned, is a way to boot up in a complete Windows environment. Rather than do that, I run W7 on a virtual machine using VMware Fusion. Parallels is similar product that allows the use of a virtual machine with another OS inside a Mac environment. With both products, you can actually have virtual machines running more than one OS, say different versions of Windows as well as Linux.

Among other things, the virtual machine will let you easily switch between OSs on the fly, and even cut and paste between them. It's a perfectly good solution for me and many others who, for one reason or the other, need/want to run Windows on Mac hardware.