Parallels makes software for Mac computers that allows you to install Windows and run Windows apps from OS X without rebooting. The latest version of Parallels adds experimental support for Windows 8.
Microsoft released  developer preview of Windows 8 recently. It features a dramatically redesigned start menu and new “Metro style” applications with a full-screen view and touch-friendly user interface.
Parallels Desktop build 7.0.14924 also offers improved copatibility with Quicken 2011, better support for AutoDesk 3ds Max 2012, and CPU usage improvements.
Parallels Desktop 7 for Mac costs $80, but there’s a 14 day free trial available. The Windows 8 Developer Preview is available as a free download.
You can probably also install Windows 8 on a Mac using the built-in Boot Camp feature, but that would require you to reboot your computer every time you want to switch between OS X and Windows.