Parallels Desktop is an environment for virtual machines on Mac OS X. Michael Verdi demonstrates some interesting coming features of Parallels in his screencast of Parallels Desktop Beta

He runs a virtual Windows PC in "coherence mode" where single Windows applications appear directly on the Mac OS desktop. The Parallels Beta makes it possible to drag and drop files between Windows Explorer and Finder and also use the clipboard between Windows and Mac applications. With these new features, Parallels really blurs the borders between the guest and the host OS, making it easy to use the best of both worlds without noticing.