According to an article on MacRumors.com, Leopard, the next version of OS X may include virtualization software, code named Chameleon, that will allow Mac’s to run more than one operating system at the SAME TIME!
While Booting Windows XP on Intel Macs is now possible thanks to two hackers named “narf2006” and “blanka”, many users look forward to using a virtual Windows XP environment alongside Mac OS X. This sort of side-by-side existence would prevent the need for rebooting to use a particular application like in the System 6 and System 7 days. When you need to open that Windows app just instantaneously switch over to Windows. When you are done, go back to OS X.